/* ============================================
   TRLE Texture Tools — VS Code Dark + Orange
   ============================================ */

:root {
    --bg-primary: #1e1e1e;
    --bg-secondary: #252526;
    --bg-tertiary: #2d2d30;
    --bg-input: #3c3c3c;
    --bg-hover: #404040;
    --bg-card: #2d2d30;
    --border: #3e3e42;
    --border-light: #555;
    --text-primary: #d4d4d4;
    --text-secondary: #969696;
    --text-muted: #6e6e6e;
    --accent: #e8852a;
    --accent-hover: #f09030;
    --accent-dim: #c06a1a;
    --accent-bg: rgba(232, 133, 42, 0.12);
    --accent-border: rgba(232, 133, 42, 0.3);
    --danger: #f44747;
    --success: #4ec94e;
    --warning: #cca700;
    --info: #3794ff;
    --scrollbar-bg: #1e1e1e;
    --scrollbar-thumb: #424242;
    --shadow: 0 2px 8px rgba(0,0,0,0.4);
    --radius: 6px;
    --radius-sm: 4px;
    --transition: 0.15s ease;
}

/* ---- Light theme (toggle) ---- */
html[data-theme="light"] {
    --bg-primary: #f3f3f3;
    --bg-secondary: #ffffff;
    --bg-tertiary: #e8e8e8;
    --bg-input: #ffffff;
    --bg-hover: #e0e0e0;
    --bg-card: #ffffff;
    --border: #d2d2d2;
    --border-light: #b0b0b0;
    --text-primary: #1f1f1f;
    --text-secondary: #5a5a5a;
    --text-muted: #888888;
    --accent-bg: rgba(232, 133, 42, 0.14);
    --accent-border: rgba(232, 133, 42, 0.45);
    --scrollbar-bg: #e4e4e4;
    --scrollbar-thumb: #c2c2c2;
    --shadow: 0 2px 8px rgba(0,0,0,0.15);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

/* Root font-size is driven by the UI-scale control (default 14px). */
html { font-size: 14px; }

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
    overflow-x: hidden;
}

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--scrollbar-bg); }
::-webkit-scrollbar-thumb { background: var(--scrollbar-thumb); border-radius: 5px; }
::-webkit-scrollbar-thumb:hover { background: #555; }

/* ---- Header ---- */
.app-header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    flex-direction: column;
}

/* Row 1: Logo + Group buttons + Help */
.header-top {
    display: flex;
    align-items: center;
    padding: 0 20px;
    height: 48px;
    gap: 0;
    border-bottom: 1px solid var(--border);
}

.app-header .logo {
    font-size: 1rem;
    font-weight: 700;
    color: var(--accent);
    white-space: nowrap;
    margin-right: 20px;
    letter-spacing: 0.3px;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    gap: 8px;
}
.app-header .logo .logo-mark {
    flex-shrink: 0;
    display: block;
}
/* Tutorial: make the "Back to the tool" button stand out (orange).
   Uses .ctrl-btn.tut-back-btn so it beats `.ctrl-btn { background:none }`. */
.ctrl-btn.tut-back-btn {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
    font-weight: 600;
}
.ctrl-btn.tut-back-btn:hover { background: #f09030; border-color: #f09030; color: #fff; }

/* ---- Header accessibility controls (theme + UI scale) ---- */
.app-controls {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-left: auto;
    flex-shrink: 0;
}
.controls-label {
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    margin-right: 2px;
    white-space: nowrap;
}
.ui-scale {
    display: flex;
    align-items: center;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
}
/* Unified segmented A− | A | A+ control — equal-width cells */
.ui-scale .ctrl-btn {
    border: none;
    border-radius: 0;
    font-weight: 600;
    font-variant-numeric: tabular-nums;
    width: 32px;
    min-width: 32px;
    padding: 0;
}
.ui-scale .ctrl-btn + .ctrl-btn { border-left: 1px solid var(--border); }
.ctrl-btn {
    background: none;
    border: 1px solid var(--border);
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    height: 28px;
    min-width: 30px;
    padding: 0 9px;
    cursor: pointer;
    font-size: 0.82rem;
    line-height: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color var(--transition), border-color var(--transition), background var(--transition);
}
.ctrl-btn:hover { color: var(--accent); background: var(--accent-bg); }
.ui-scale .ctrl-btn:hover { border-color: transparent; }
.ctrl-btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.theme-toggle { font-size: 1rem; width: 32px; min-width: 32px; padding: 0; }

/* Group bar — switches which tool section is active */
.group-bar {
    display: flex;
    gap: 2px;
    flex: 1;
    height: 100%;
    overflow-x: auto;
    scrollbar-width: none;
}
.group-bar::-webkit-scrollbar { display: none; }

.group-btn {
    background: none;
    border: none;
    border-bottom: 3px solid transparent;
    color: var(--text-secondary);
    font-size: 0.88rem;
    font-weight: 500;
    padding: 0 18px;
    cursor: pointer;
    white-space: nowrap;
    transition: color var(--transition), border-color var(--transition), background var(--transition);
    height: 100%;
    display: flex;
    align-items: center;
    gap: 6px;
    letter-spacing: 0.02em;
}
.group-btn:hover { color: var(--text-primary); background: var(--bg-tertiary); }
.group-btn.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
    font-weight: 600;
}

/* Help button — pinned right */
.help-btn {
    background: none;
    border: 1px solid var(--border);
    border-radius: 50%;
    width: 28px;
    height: 28px;
    font-size: 0.85rem;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-left: 12px;
    flex-shrink: 0;
    transition: color var(--transition), border-color var(--transition), background var(--transition);
}
.help-btn:hover {
    color: var(--accent);
    border-color: var(--accent);
    background: var(--accent-bg);
}

/* Row 2: Sub-tabs */
.tab-bar {
    display: flex;
    gap: 0;
    height: 36px;
    overflow-x: auto;
    scrollbar-width: none;
    padding: 0 20px;
    background: var(--bg-primary);
}
.tab-bar::-webkit-scrollbar { display: none; }

/* Tab group wrapper — swapped on group switch */
.tab-group {
    display: flex;
    height: 100%;
}

.tab-btn {
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-secondary);
    font-size: 0.82rem;
    padding: 0 14px;
    cursor: pointer;
    white-space: nowrap;
    transition: color var(--transition), border-color var(--transition), background var(--transition);
    height: 100%;
    display: flex;
    align-items: center;
    gap: 5px;
}
.tab-btn:hover { color: var(--text-primary); background: var(--bg-tertiary); }
.tab-btn.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
}
.tab-btn .tab-icon { font-size: 0.95rem; }

/* ---- Main Content ---- */
.app-main {
    max-width: 1400px;
    margin: 0 auto;
    padding: 24px 20px 60px;
}

.tab-content { display: none; }
.tab-content.active { display: block; animation: tabFadeIn 0.22s ease both; }

/* ---- Subtle UI motion ----
   Scoped to navigation + controls only — never the tool content/tile grids,
   which would be distracting while rearranging. */
@keyframes tabFadeIn {
    from { opacity: 0; transform: translateY(4px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* Tactile press feedback on navigation + buttons */
.group-btn:active,
.tab-btn:active           { transform: scale(0.96); }
.btn:active:not(:disabled){ transform: scale(0.97); }

/* The active-tab underline animates in rather than snapping */
.tab-btn, .group-btn { transition: color var(--transition), border-color var(--transition), background var(--transition), transform 0.08s ease; }

@media (prefers-reduced-motion: reduce) {
    .tab-content.active { animation: none; }
    *, *::before, *::after {
        animation-duration: 0.001ms !important;
        transition-duration: 0.001ms !important;
    }
}

/* ---- Cards ---- */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 20px;
    margin-bottom: 16px;
}
.card-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 8px;
}

/* ---- Notices ---- */
.notice {
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    margin-bottom: 16px;
    font-size: 0.85rem;
    display: flex;
    align-items: flex-start;
    gap: 10px;
    line-height: 1.5;
}
.notice-icon { font-size: 1.1rem; flex-shrink: 0; margin-top: 1px; }
.notice-info {
    background: rgba(55, 148, 255, 0.08);
    border: 1px solid rgba(55, 148, 255, 0.25);
    color: #8ec8ff;
}
.notice-warning {
    background: rgba(204, 167, 0, 0.08);
    border: 1px solid rgba(204, 167, 0, 0.25);
    color: #ffe066;
}
.notice-tomb-engine {
    background: var(--accent-bg);
    border: 1px solid var(--accent-border);
    color: #f0c080;
}

/* ---- Credit Banner (JohnnyJF10 algorithm credit) ---- */
.credit-banner {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 16px;
    margin-bottom: 14px;
    background: linear-gradient(90deg, rgba(79,163,224,0.12) 0%, rgba(79,163,224,0.05) 100%);
    border-left: 4px solid #4fa3e0;
    border-radius: 0 var(--radius) var(--radius) 0;
    color: #a8ccec;
    font-size: 0.85rem;
}
.credit-banner .credit-icon { font-size: 1rem; flex-shrink: 0; }
.credit-banner a {
    color: #7ec8f5;
    font-weight: 700;
    text-decoration: none;
}
.credit-banner a:hover { color: #aee0ff; text-decoration: underline; }

/* ---- Collapsible Sections ---- */
.collapsible-header {
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 0;
    user-select: none;
    color: var(--accent);
    font-weight: 500;
    font-size: 0.9rem;
}
.collapsible-header:hover { color: var(--accent-hover); }
.collapsible-header .arrow {
    transition: transform var(--transition);
    font-size: 0.7rem;
}
.collapsible-header.open .arrow { transform: rotate(90deg); }
.collapsible-body {
    display: none;
    padding: 8px 0 8px 8px;
}
.collapsible-body.open { display: block; }

/* ---- Map Explanations ---- */
.map-explanation {
    padding: 10px 14px;
    margin-bottom: 8px;
    background: var(--bg-secondary);
    border-left: 3px solid var(--accent);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    font-size: 0.82rem;
    color: var(--text-secondary);
    line-height: 1.6;
}
.map-explanation strong { color: var(--accent); font-weight: 600; }
.map-explanation .map-title {
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.88rem;
    margin-bottom: 4px;
}
.map-explanation .map-examples {
    color: var(--text-muted);
    font-style: italic;
    margin-top: 4px;
}

/* ---- Form Controls ---- */
.form-row {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 10px;
    flex-wrap: wrap;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 500;
}

select, input[type="number"], input[type="text"] {
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    padding: 6px 10px;
    font-size: 0.85rem;
    outline: none;
    transition: border-color var(--transition);
}
select:focus, input[type="number"]:focus, input[type="text"]:focus {
    border-color: var(--accent);
}
select { cursor: pointer; padding-right: 24px; }
input[type="number"] { width: 80px; }

/* Range slider */
input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    height: 4px;
    background: var(--bg-input);
    border-radius: 2px;
    outline: none;
    cursor: pointer;
}
input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 14px; height: 14px;
    border-radius: 50%;
    background: var(--accent);
    cursor: pointer;
    border: 2px solid var(--bg-primary);
}
input[type="range"]::-moz-range-thumb {
    width: 14px; height: 14px;
    border-radius: 50%;
    background: var(--accent);
    cursor: pointer;
    border: 2px solid var(--bg-primary);
}

/* Checkboxes */
.checkbox-row {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    font-size: 0.85rem;
}
.checkbox-row input[type="checkbox"] {
    accent-color: var(--accent);
    width: 16px;
    height: 16px;
    cursor: pointer;
}

/* ---- Buttons ---- */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    border: 1px solid transparent;
    transition: all var(--transition);
    white-space: nowrap;
}
.btn-primary {
    background: var(--accent);
    color: #fff;
}
.btn-primary:hover { background: var(--accent-hover); transform: translateY(-1px); box-shadow: var(--shadow); }
.btn-primary:active { transform: translateY(0); }

.btn-secondary {
    background: var(--bg-input);
    color: var(--text-primary);
    border-color: var(--border);
}
.btn-secondary:hover { background: var(--bg-hover); border-color: var(--border-light); }

.btn-sm { padding: 5px 10px; font-size: 0.8rem; }
.btn-danger { background: #5c2020; color: #f44747; border-color: #7c2020; }
.btn-danger:hover { background: #6c2525; }

.btn:disabled { opacity: 0.4; cursor: not-allowed; transform: none !important; }

/* Busy buttons stay legible (not dimmed) and show a spinner */
.btn.btn-busy { opacity: 1; cursor: progress; }
.btn-busy.btn-primary { background: var(--accent-dim); }
.btn-spinner {
    display: inline-block;
    width: 13px;
    height: 13px;
    margin-right: 7px;
    vertical-align: -2px;
    border: 2px solid currentColor;
    border-top-color: transparent;
    border-radius: 50%;
    animation: btnSpin 0.6s linear infinite;
}
@keyframes btnSpin { to { transform: rotate(360deg); } }
@media (prefers-reduced-motion: reduce) {
    .btn-spinner { animation-duration: 1.6s; }
}

/* ---- Keyboard focus rings (a11y) ----
   Only shown for keyboard users via :focus-visible, never on mouse click. */
:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}
.at-cell:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
    box-shadow: 0 0 0 2px var(--accent);
    z-index: 1;
}
.at-ctx button:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: -2px;
}
/* Lighter ring on the orange primary buttons for contrast */
.btn-primary:focus-visible {
    outline-color: #fff;
}

/* ---- Atlas grid header + undo/redo toolbar ---- */
.at-grid-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 12px;
}
.at-toolbar {
    display: flex;
    gap: 6px;
    flex-shrink: 0;
}

/* ---- Upload Area ---- */
.upload-area {
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 32px;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    background: var(--bg-secondary);
    position: relative;
}
.upload-area:hover, .upload-area.drag-over {
    border-color: var(--accent);
    background: var(--accent-bg);
}
.upload-area .upload-icon { font-size: 2rem; margin-bottom: 8px; }
.upload-area .upload-text { color: var(--text-secondary); font-size: 0.85rem; }
.upload-area .upload-text span { color: var(--accent); font-weight: 500; }
.upload-area input[type="file"] {
    position: absolute; inset: 0; opacity: 0; cursor: pointer;
}
.upload-area .preview-img {
    max-width: 200px;
    max-height: 200px;
    border-radius: var(--radius-sm);
    margin-top: 8px;
    image-rendering: pixelated;
}

.upload-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

/* ---- Tile Grid ---- */
.tile-grid {
    display: grid;
    gap: 6px;
    margin: 12px 0;
    max-height: 600px;
    overflow-y: auto;
    padding: 4px;
}
#ac-tile-grid {
    max-height: 75vh;
}
.tile-cell {
    position: relative;
    aspect-ratio: 1;
    background: var(--bg-secondary);
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    cursor: pointer;
    transition: border-color var(--transition);
}
.tile-cell:hover { border-color: var(--accent); }
.tile-cell.selected { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent); }
.tile-cell img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    image-rendering: pixelated;
}
.tile-cell .tile-label {
    position: absolute;
    bottom: 0; left: 0; right: 0;
    background: rgba(0,0,0,0.7);
    font-size: 0.7rem;
    padding: 2px 4px;
    text-align: center;
    color: var(--text-secondary);
}
.tile-cell .tile-index {
    position: absolute;
    top: 2px; left: 4px;
    font-size: 0.65rem;
    color: var(--accent);
    font-weight: 700;
    text-shadow: 0 1px 2px #000;
}
.tile-cell select {
    position: absolute;
    bottom: 0; left: 0; right: 0;
    width: 100%;
    border-radius: 0;
    font-size: 0.7rem;
    padding: 3px 4px;
    background: rgba(30,30,30,0.9);
    border: none;
    border-top: 1px solid var(--border);
}

/* ---- Results Grid ---- */
.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 8px;
    margin: 12px 0;
}
.result-cell {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
    text-align: center;
    cursor: pointer;
    transition: border-color var(--transition);
}
.result-cell:hover { border-color: var(--accent); }
.result-cell canvas, .result-cell img {
    width: 100%;
    aspect-ratio: 1;
    object-fit: cover;
    display: block;
    image-rendering: pixelated;
}
.result-cell .result-label {
    padding: 4px;
    font-size: 0.7rem;
    color: var(--text-secondary);
    border-top: 1px solid var(--border);
    background: var(--bg-tertiary);
}

/* ---- Sub-tabs (for map type results) ---- */
.sub-tab-bar {
    display: flex;
    gap: 0;
    border-bottom: 1px solid var(--border);
    margin-bottom: 12px;
    overflow-x: auto;
}
.sub-tab-btn {
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-secondary);
    font-size: 0.8rem;
    padding: 8px 14px;
    cursor: pointer;
    white-space: nowrap;
    transition: color var(--transition), border-color var(--transition);
}
.sub-tab-btn:hover { color: var(--text-primary); }
.sub-tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }
.sub-tab-content { display: none; }
.sub-tab-content.active { display: block; animation: tabFadeIn 0.18s ease both; }

/* ---- Progress Bar ---- */
.progress-bar-container {
    width: 100%;
    height: 4px;
    background: var(--bg-input);
    border-radius: 2px;
    margin: 12px 0;
    overflow: hidden;
    display: none;
}
.progress-bar-container.active { display: block; }
.progress-bar-fill {
    height: 100%;
    background: var(--accent);
    border-radius: 2px;
    width: 0%;
    transition: width 0.3s ease;
}

/* ---- Map Checkboxes Row ---- */
.map-checks {
    display: flex;
    flex-wrap: wrap;
    gap: 16px;
    padding: 8px 0;
}
.map-checks .checkbox-row { min-width: 100px; }

/* ---- Set All Row ---- */
.set-all-row {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 0;
    border-top: 1px solid var(--border);
    margin-top: 8px;
}
.set-all-row label { font-weight: 600; color: var(--text-primary); }

/* ---- Advanced Editor ---- */
.editor-layout {
    display: grid;
    grid-template-columns: 1fr 350px;
    gap: 16px;
}
.editor-preview {
    aspect-ratio: 1;
    background: #111;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
    position: relative;
}
.editor-preview canvas {
    width: 100%;
    height: 100%;
}

.param-panel {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 12px;
    margin-bottom: 8px;
}
.param-panel .panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
    cursor: pointer;
}
.param-panel .panel-title {
    font-weight: 600;
    font-size: 0.85rem;
    color: var(--accent);
}
.param-row {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 6px;
}
.param-row label {
    min-width: 90px;
    font-size: 0.78rem;
}
.param-row input[type="range"] { flex: 1; }
.param-row .param-value {
    min-width: 35px;
    text-align: right;
    font-size: 0.78rem;
    color: var(--accent);
    font-weight: 500;
}

/* Frequency EQ */
.freq-eq {
    display: flex;
    align-items: flex-end;
    gap: 6px;
    height: 100px;
    padding: 8px 0;
    justify-content: center;
}
.freq-eq .eq-band {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}
.freq-eq .eq-band input[type="range"] {
    writing-mode: vertical-lr;
    direction: rtl;
    height: 70px;
    width: 20px;
}
.freq-eq .eq-band .eq-label {
    font-size: 0.6rem;
    color: var(--text-muted);
}

/* ---- Transition Direction Grid ---- */
.trans-dir-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
}
.trans-dir-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 5px;
    padding: 12px 6px;
    background: var(--bg-secondary);
    border: 2px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    color: var(--text-secondary);
    font-size: 0.78rem;
    font-weight: 500;
    transition: all 0.15s ease;
    line-height: 1;
}
.trans-dir-btn:hover {
    background: var(--bg-tertiary);
    border-color: var(--accent);
    color: var(--text-primary);
}
.trans-dir-btn.active {
    background: rgba(227, 134, 36, 0.12);
    border-color: var(--accent);
    color: var(--accent);
    font-weight: 700;
}
.trans-dir-icon {
    font-size: 1.3rem;
    line-height: 1;
}
@media (max-width: 700px) {
    .trans-dir-grid { grid-template-columns: repeat(4, 1fr); }
}

/* ---- Transition Batch Preview Grid ---- */
.trans-batch-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}
.trans-batch-cell {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 5px;
}
.trans-batch-cell canvas {
    width: 100%;
    height: auto;
    aspect-ratio: 1;
    transition: border-color 0.15s ease;
}
.trans-batch-cell canvas:hover {
    border-color: var(--accent) !important;
}
.trans-batch-label {
    font-size: 0.72rem;
    color: var(--text-secondary);
    font-weight: 500;
}
@media (max-width: 700px) {
    .trans-batch-grid { grid-template-columns: repeat(2, 1fr); }
}

/* ---- Download Bar ---- */
.download-bar {
    display: flex;
    gap: 8px;
    align-items: center;
    padding: 12px 0;
    flex-wrap: wrap;
}

/* ---- Parameter Hints ---- */
.param-hint {
    font-size: 0.72rem;
    color: var(--text-secondary);
    opacity: 0.7;
    padding: 0 4px 6px 4px;
    line-height: 1.3;
    border-bottom: 1px solid var(--border);
    margin-bottom: 6px;
}
.param-hint:last-child { border-bottom: none; margin-bottom: 0; }

/* ---- Map Thumbnail Strip ---- */
.map-thumb-strip {
    display: flex;
    gap: 6px;
    margin-top: 8px;
    overflow-x: auto;
    padding: 4px 0;
}
.map-thumb {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
    cursor: pointer;
    padding: 4px;
    border-radius: var(--radius);
    border: 2px solid transparent;
    transition: border-color 0.15s, background 0.15s;
    flex-shrink: 0;
    min-width: 56px;
}
.map-thumb:hover {
    background: var(--bg-tertiary);
    border-color: var(--border);
}
.map-thumb.active {
    border-color: var(--accent);
    background: rgba(227, 134, 36, 0.1);
}
.map-thumb-canvas {
    width: 48px;
    height: 48px;
    border-radius: 3px;
    background: var(--bg-primary);
    image-rendering: pixelated;
}
.map-thumb span {
    font-size: 0.65rem;
    color: var(--text-secondary);
    text-align: center;
    white-space: nowrap;
}
.map-thumb.active span {
    color: var(--accent);
    font-weight: 600;
}

/* ---- Help Overlay ---- */
.help-overlay {
    position: fixed;
    inset: 0;
    z-index: 1000;
    background: rgba(0,0,0,0.5);
    display: flex;
    justify-content: flex-end;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
}
.help-overlay.open {
    opacity: 1;
    pointer-events: all;
}

.help-panel {
    background: var(--bg-secondary);
    border-left: 1px solid var(--border);
    width: 400px;
    max-width: 95vw;
    height: 100%;
    display: flex;
    flex-direction: column;
    transform: translateX(100%);
    transition: transform 0.25s ease;
    box-shadow: -4px 0 24px rgba(0,0,0,0.4);
}
.help-overlay.open .help-panel {
    transform: translateX(0);
}

.help-panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 20px;
    border-bottom: 1px solid var(--border);
    flex-shrink: 0;
}
.help-panel-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
}
.help-close-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1rem;
    cursor: pointer;
    padding: 4px 8px;
    border-radius: var(--radius-sm);
    transition: color var(--transition), background var(--transition);
}
.help-close-btn:hover { color: var(--text-primary); background: var(--bg-hover); }

.help-panel-body {
    overflow-y: auto;
    padding: 16px 20px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.help-section {
    padding: 14px 0;
    border-bottom: 1px solid var(--border);
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.6;
}
.help-section:last-child { border-bottom: none; }

.help-section-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.help-link {
    color: var(--accent);
    text-decoration: none;
}
.help-link:hover { text-decoration: underline; color: var(--accent-hover); }

.help-code-block {
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 8px 12px;
    margin: 8px 0;
    font-size: 0.82rem;
}
.help-code-label {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    margin-bottom: 4px;
}
.help-code-block code {
    color: var(--accent);
    font-family: 'Consolas', 'Fira Mono', 'Menlo', monospace;
}

/* ---- Toast ---- */
.toast {
    position: fixed;
    top: 60px;                 /* just below the sticky header */
    left: 50%;
    display: flex;
    align-items: center;
    gap: 9px;
    max-width: min(420px, calc(100vw - 48px));
    background: var(--bg-tertiary);
    border: 1px solid var(--accent);
    border-left-width: 4px;
    color: var(--text-primary);
    padding: 12px 18px;
    border-radius: var(--radius);
    font-size: 0.85rem;
    line-height: 1.4;
    box-shadow: var(--shadow);
    z-index: 9999;
    transform: translate(-50%, -16px);
    opacity: 0;
    transition: transform 0.3s ease, opacity 0.3s ease;
}
.toast.show { transform: translate(-50%, 0); opacity: 1; }
.toast .toast-icon { flex-shrink: 0; font-size: 1rem; }
.toast .toast-msg { min-width: 0; }
.toast-success { border-color: var(--success); }
.toast-error   { border-color: var(--danger); }
.toast-warning { border-color: var(--warning); }
.toast-info    { border-color: var(--info); }

/* ---- Responsive ---- */
@media (max-width: 900px) {
    .editor-layout {
        grid-template-columns: 1fr;
    }
    .upload-row {
        grid-template-columns: 1fr;
    }
}
@media (max-width: 600px) {
    .app-header { padding: 0 10px; }
    .tab-btn { padding: 0 10px; font-size: 0.78rem; }
    .app-main { padding: 16px 10px 40px; }
    .mask-groups { grid-template-columns: 1fr; }
}

/* ============================================================
   Spritefont Maker
   ============================================================ */
.sf-source-toggle {
    display: inline-flex;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    overflow: hidden;
}
.sf-source-btn {
    background: none;
    border: none;
    padding: 6px 16px;
    cursor: pointer;
    color: var(--text-secondary);
    font-size: 0.82rem;
    transition: background var(--transition), color var(--transition);
}
.sf-source-btn:hover { background: var(--bg-tertiary); }
.sf-source-btn.active {
    background: var(--accent);
    color: #fff;
}
.sf-range-checks {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    padding: 4px 0;
}
.sf-custom-ranges {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-top: 6px;
}
.sf-custom-range-tag {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 20px;
    padding: 2px 10px 2px 12px;
    font-size: 0.78rem;
    color: var(--text-secondary);
}
.sf-custom-range-tag button {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-secondary);
    font-size: 0.85rem;
    padding: 0 2px;
    line-height: 1;
}
.sf-preview-wrap {
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: auto;
    background: #111;
    padding: 8px;
    min-height: 60px;
}
.sf-atlas-canvas {
    display: block;
    image-rendering: pixelated;
    max-width: 100%;
}
.sf-test-canvas {
    display: block;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: #111;
    width: 100%;
    image-rendering: pixelated;
}

/* ============================================================
   Advanced Material Editor — Per-tile accordion
   ============================================================ */
#adv-tile-grid {
    max-height: none;
}
.adv-tile-slot {
    grid-column: 1 / -1;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
    transition: border-color var(--transition);
}
.adv-tile-slot:has(.adv-slot-body.open) {
    border-color: var(--accent);
}
.adv-slot-header {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 12px;
    cursor: pointer;
    background: var(--bg-primary);
    user-select: none;
}
.adv-slot-header:hover {
    background: var(--bg-secondary);
}
.adv-slot-thumb {
    width: 56px;
    height: 56px;
    object-fit: cover;
    image-rendering: pixelated;
    border-radius: var(--radius-sm);
    flex-shrink: 0;
    border: 1px solid var(--border);
}
.adv-slot-index {
    font-size: 0.75rem;
    color: var(--accent);
    font-weight: 700;
    min-width: 28px;
}
.adv-slot-badge {
    font-size: 0.75rem;
    color: #4caf50;
    font-weight: 700;
    background: rgba(76,175,80,0.15);
    border: 1px solid rgba(76,175,80,0.4);
    border-radius: 3px;
    padding: 1px 5px;
}
.adv-slot-chevron {
    margin-left: auto;
    font-size: 0.8rem;
    color: var(--text-secondary);
    transition: transform var(--transition);
}
.adv-slot-body {
    display: none;
    padding: 14px 16px;
    border-top: 1px solid var(--border);
}
.adv-slot-body.open {
    display: block;
}
.adv-diffuse-display {
    display: block;
    width: 128px;
    height: 128px;
    object-fit: cover;
    image-rendering: pixelated;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    margin-bottom: 12px;
}
.adv-control-label {
    display: block;
    font-size: 0.78rem;
    color: var(--text-secondary);
    margin-bottom: 4px;
    margin-top: 10px;
}
.adv-control-row {
    display: flex;
    flex-direction: column;
    margin-bottom: 4px;
}
.adv-preset-sel {
    width: 100%;
    max-width: 320px;
}
/* ---- Advanced editor: map type tabs ---- */
.adv-map-tabs {
    display: flex;
    flex-wrap: wrap;
    gap: 2px;
    border-bottom: 1px solid var(--border);
    margin-top: 14px;
}
.adv-map-tab-btn {
    padding: 4px 11px;
    border: 1px solid transparent;
    border-bottom: none;
    border-radius: var(--radius-sm) var(--radius-sm) 0 0;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.8rem;
    cursor: pointer;
    margin-bottom: -1px;
    transition: color 0.12s;
}
.adv-map-tab-btn:hover { color: var(--text-primary); }
.adv-map-tab-btn.active {
    background: var(--bg-secondary);
    border-color: var(--border);
    border-bottom-color: var(--bg-secondary);
    color: var(--text-primary);
}
.adv-map-tab-btn.map-disabled {
    opacity: 0.4;
    text-decoration: line-through;
}
.adv-map-tab-panels {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-top: none;
    border-radius: 0 0 var(--radius-sm) var(--radius-sm);
    padding: 10px 12px 8px;
    margin-bottom: 10px;
}
.adv-map-tab-panel { display: none; }
.adv-map-tab-panel.active { display: block; }
.adv-include-row {
    display: flex;
    align-items: center;
    gap: 6px;
    margin-bottom: 10px;
    font-size: 0.84rem;
    color: var(--text-primary);
}
.adv-include-row label { cursor: pointer; }
.adv-param-row {
    display: flex;
    align-items: center;
    gap: 8px;
    margin: 4px 0 1px;
}
.adv-param-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    width: 72px;
    flex-shrink: 0;
}
.adv-param-slider {
    flex: 1;
    min-width: 80px;
    accent-color: var(--accent);
}
.adv-param-val {
    font-size: 0.8rem;
    width: 36px;
    text-align: right;
    font-variant-numeric: tabular-nums;
    color: var(--text-secondary);
    flex-shrink: 0;
}
.adv-param-help {
    font-size: 0.73rem;
    color: var(--text-secondary);
    opacity: 0.8;
    padding-left: 80px;
    margin-top: 1px;
    margin-bottom: 7px;
    line-height: 1.3;
}
/* ---- Generate row with live preview toggle ---- */
.adv-gen-row {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 14px;
    flex-wrap: wrap;
}
.adv-check-label {
    display: flex;
    align-items: center;
    gap: 4px;
    font-size: 0.82rem;
    color: var(--text-primary);
    cursor: pointer;
    user-select: none;
}
.adv-live-label { color: var(--text-secondary); }
/* ---- Preview lighting note ---- */
.adv-preview-note {
    font-size: 0.78rem;
    color: var(--text-secondary);
    border-top: 1px solid var(--border);
    padding-top: 8px;
    margin-top: 4px;
    margin-bottom: 6px;
    line-height: 1.4;
}
.adv-preview-placeholder {
    min-height: 0;
    border-radius: var(--radius-sm);
    overflow: hidden;
}
.adv-preview-placeholder canvas {
    display: block;
    width: 100%;
    max-width: 512px;
    height: auto;
    image-rendering: pixelated;
    border-radius: var(--radius-sm);
}
.adv-light-controls {
    display: flex;
    flex-direction: column;
    gap: 6px;
    margin-top: 10px;
}
.adv-slider-row {
    display: flex;
    align-items: center;
    gap: 8px;
}
.adv-slider-row .adv-control-label {
    width: 22px;
    flex-shrink: 0;
}
.adv-slider-row input[type=range] {
    flex: 1;
    min-width: 120px;
    accent-color: var(--accent);
}
.adv-slider-val {
    width: 36px;
    text-align: right;
    font-size: 0.82rem;
    color: var(--text-secondary);
    font-variant-numeric: tabular-nums;
    flex-shrink: 0;
}

/* ============ WebGL Compat Banner ============ */
#webgl-compat-banner {
    position: sticky;
    top: 0;
    z-index: 9999;
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 16px;
    background: #5c3200;
    border-bottom: 1px solid #8a5200;
    color: #ffd9a3;
    font-size: 0.875rem;
    line-height: 1.4;
}
#webgl-compat-banner[data-level='error'] {
    background: #5c0000;
    border-bottom-color: #8a0000;
    color: #ffd0d0;
}
.compat-icon { flex-shrink: 0; }
.compat-message { flex: 1; }
.compat-dismiss {
    background: none;
    border: 1px solid currentColor;
    border-radius: 3px;
    color: inherit;
    cursor: pointer;
    flex-shrink: 0;
    font-size: 0.8rem;
    opacity: 0.7;
    padding: 2px 8px;
}
.compat-dismiss:hover { opacity: 1; }

/* ---- Seamless Texture Maker Preview Canvas ---- */
.sm-hint {
    font-size: 0.75rem;
    color: var(--text-secondary);
    margin-top: 6px;
    line-height: 1.4;
}
.sm-preview-canvas {
    display: block;
    width: 512px;
    height: 512px;
    max-width: 100%;
    margin: 0 auto;
    border: 1px solid var(--border);
    border-radius: 8px;
    image-rendering: auto;
    background: repeating-conic-gradient(var(--bg-tertiary) 0% 25%, transparent 0% 50%) 50% / 20px 20px;
}
.at-fade-canvas {
    display: block;
    border-radius: 6px;
    border: 1px solid var(--border);
    image-rendering: pixelated;
    touch-action: none;
    cursor: crosshair;
    /* checkerboard so transparent areas read clearly */
    background: repeating-conic-gradient(#888 0% 25%, #bbb 0% 50%) 50% / 16px 16px;
}

/* ============================================================
   ATLAS TOOL — grid, context menu, modals
   ============================================================ */

/* ---- Element grid ---- */
.at-grid {
    display: grid;
    gap: 6px;
    margin-top: 14px;
    grid-template-columns: repeat(auto-fill, minmax(96px, 1fr));
}
.at-cell {
    position: relative;
    border: 2px solid var(--border);
    border-radius: 6px;
    overflow: hidden;
    cursor: pointer;
    background: var(--bg-secondary);
    user-select: none;
}
.at-cell:hover { border-color: var(--accent); }
.at-cell.selected { border-color: var(--accent); box-shadow: 0 0 0 1px var(--accent); }
.at-cell.locked {
    border-color: #4ec9b0;
    box-shadow: 0 0 0 2px #4ec9b0;
}
.at-cell.pickable { border-color: var(--border-light); }
/* Layout (rows/columns) control */
.at-layout-row {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 4px 0 12px;
    flex-wrap: wrap;
}
.at-layout-label {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-muted);
    font-weight: 700;
}
.at-layout-row label {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 0.82rem;
    color: var(--text-secondary);
}
.at-layout-row input[type="number"] { width: 60px; }
.at-layout-x { color: var(--text-muted); }
.at-layout-note { font-size: 0.78rem; color: var(--text-muted); }
/* "or" separator + add-tile cell (Phase A: blank atlas / dynamic tiles) */
.at-or-sep {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin: 16px 0 8px;
    position: relative;
}
.at-add-cell {
    aspect-ratio: 1;
    border: 2px dashed var(--border);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    color: var(--text-secondary);
    transition: border-color var(--transition), color var(--transition), background var(--transition);
}
.at-add-cell:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-bg); }
.at-add-cell:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.at-add-plus { font-size: 1.7rem; line-height: 1; }

.at-cell.at-dragging { opacity: 0.4; }
.at-cell.at-drop-target {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px var(--accent);
}
.at-cell canvas {
    width: 100%;
    display: block;
    image-rendering: pixelated;
    aspect-ratio: 1;
}
.at-cell .at-idx {
    position: absolute; top: 3px; left: 5px;
    font-size: 0.65rem; color: #fff;
    background: rgba(0,0,0,0.55);
    border-radius: 3px; padding: 1px 4px;
    pointer-events: none;
}
.at-cell .at-badges {
    position: absolute; top: 3px; right: 4px;
    display: flex; gap: 3px;
    pointer-events: none;
}
.at-badge {
    font-size: 0.6rem; font-weight: 700;
    border-radius: 3px; padding: 1px 4px;
    color: #1e1e1e;
}
.at-badge-s { background: #4ec9b0; }
.at-badge-t { background: var(--accent); }
.at-cell .at-mat-label {
    position: absolute; bottom: 0; left: 0; right: 0;
    font-size: 0.62rem; text-align: center;
    background: rgba(0,0,0,0.6); color: var(--text-secondary);
    padding: 1px 2px;
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
    pointer-events: none;
}

/* ---- Pick-partner banner ---- */
.at-pick-banner {
    margin: 12px 0;
    padding: 10px 14px;
    border: 1px solid #4ec9b0;
    border-radius: 6px;
    background: rgba(78, 201, 176, 0.08);
    font-size: 0.85rem;
}

/* ---- Delete mode ---- */
.at-del-banner {
    border-color: #f44747;
    background: rgba(244, 71, 71, 0.08);
}
#at-delete-mode.active {
    border-color: #f44747;
    color: #f44747;
}
.at-del-pick .at-cell, .at-cell.at-del-pick { cursor: pointer; }
.at-cell.at-del-selected {
    outline: 3px solid #f44747;
    outline-offset: -3px;
}
.at-cell.at-del-selected::after {
    content: "✓";
    position: absolute;
    top: 3px;
    right: 4px;
    z-index: 3;
    width: 18px;
    height: 18px;
    line-height: 18px;
    text-align: center;
    font-size: 0.8rem;
    font-weight: 700;
    color: #fff;
    background: #f44747;
    border-radius: 50%;
}
/* Red danger button (delete confirmations) */
.btn.at-btn-danger {
    background: #c43b3b;
    border-color: #c43b3b;
    color: #fff;
}
.btn.at-btn-danger:hover { background: #d44; border-color: #d44; }
.btn.at-btn-danger:disabled { opacity: 0.45; cursor: not-allowed; }

/* ---- Context menu ---- */
.at-ctx {
    position: fixed;
    z-index: 1000;
    min-width: 230px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-light);
    border-radius: 6px;
    box-shadow: var(--shadow);
    padding: 4px;
}
.at-ctx button {
    display: block;
    width: 100%;
    text-align: left;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 0.85rem;
    padding: 8px 10px;
    border-radius: 4px;
    cursor: pointer;
}
.at-ctx button:hover { background: var(--bg-hover); }
.at-ctx button:disabled { opacity: 0.4; cursor: not-allowed; }
.at-ctx hr { border: none; border-top: 1px solid var(--border); margin: 4px 0; }
.at-ctx .at-ctx-danger { color: #f44747; }

/* ---- Modal overlay ---- */
.at-overlay {
    position: fixed;
    inset: 0;
    z-index: 900;
    background: rgba(0,0,0,0.6);
    display: flex;
    align-items: flex-start;
    justify-content: center;
    overflow-y: auto;
    padding: 40px 16px;
}
.at-modal {
    background: var(--bg-primary);
    border: 1px solid var(--border-light);
    border-radius: 8px;
    box-shadow: var(--shadow);
    padding: 20px;
    width: min(640px, 96vw);
}
.at-modal.at-modal-wide { width: min(760px, 96vw); }
.at-modal-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 14px;
}
.at-modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-top: 16px;
}

/* ---- Transition modal bits ---- */
.at-tr-thumb { text-align: center; font-size: 0.7rem; color: var(--text-secondary); }
.at-tr-thumb canvas {
    display: block;
    border: 1px solid var(--border);
    border-radius: 6px;
    image-rendering: pixelated;
    margin-bottom: 3px;
}
.at-tr-dirs {
    display: grid;
    grid-template-columns: repeat(8, 1fr);
    gap: 4px;
}
.at-tr-dirs .at-dir-btn {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text-primary);
    font-size: 0.7rem;
    padding: 6px 2px;
    cursor: pointer;
}
.at-tr-dirs .at-dir-btn.active {
    border-color: var(--accent);
    background: rgba(232, 133, 42, 0.15);
}

/* ---- Material modal bits ---- */
.at-mat-sliders {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px 16px;
}
.at-mat-sliders .form-group label { font-size: 0.72rem; }
.at-mat-previews {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}
.at-mat-previews .at-mat-prev {
    text-align: center;
    font-size: 0.65rem;
    color: var(--text-secondary);
}
.at-mat-previews canvas {
    width: 96px; height: 96px;
    display: block;
    border: 1px solid var(--border);
    border-radius: 4px;
    image-rendering: pixelated;
    margin-bottom: 2px;
}

/* ============================================================
   Tutorial page (tutorial.html)
   ============================================================ */
.tut-layout {
    display: grid;
    grid-template-columns: 232px 1fr;
    gap: 28px;
    max-width: 1200px;
    margin: 0 auto;
    padding: 24px 20px 80px;
    align-items: start;
}
.tut-toc {
    position: sticky;
    top: 64px;
    align-self: start;
    max-height: calc(100vh - 80px);
    overflow-y: auto;
}
.tut-toc-title {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    font-weight: 700;
    padding: 0 10px 8px;
}
.tut-toc-list { list-style: none; }
.tut-toc-list a {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 7px 10px;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.86rem;
    border-left: 2px solid transparent;
    transition: color var(--transition), background var(--transition), border-color var(--transition);
}
.tut-toc-list a:hover { color: var(--text-primary); background: var(--bg-tertiary); }
.tut-toc-list a.active {
    color: var(--accent);
    border-left-color: var(--accent);
    background: var(--accent-bg);
    font-weight: 600;
}
.tut-toc-list .toc-ico { width: 18px; text-align: center; }

.tut-main { min-width: 0; }
.tut-section {
    padding: 14px 0 28px;
    border-bottom: 1px solid var(--border);
    scroll-margin-top: 64px;
}
.tut-h2 {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.4rem;
    color: var(--text-primary);
    margin-bottom: 10px;
}
.tut-h2 .tut-ico { font-size: 1.3rem; }
.tut-what { color: var(--text-secondary); font-size: 0.95rem; line-height: 1.6; margin-bottom: 12px; }
/* Consistent emphasis everywhere: <strong> = a literal UI control/button/option
   (bold accent); <em> = conceptual emphasis (italic). */
.tut-what strong, .tut-how strong, .tut-tip strong { color: var(--accent); font-weight: 600; }
.tut-what em, .tut-how em, .tut-tip em { font-style: italic; color: inherit; }
.tut-what code, .tut-how code, .tut-tip code {
    font-family: var(--mono, ui-monospace, monospace);
    font-size: 0.85em; background: var(--accent-bg); color: var(--accent);
    padding: 0 4px; border-radius: 3px;
}
.tut-how { margin: 0 0 16px 20px; color: var(--text-secondary); font-size: 0.9rem; line-height: 1.6; }
.tut-how li { margin-bottom: 4px; }
.tut-tip {
    background: var(--accent-bg);
    border-left: 3px solid var(--accent);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    padding: 9px 14px;
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 14px;
}
.tut-open {
    display: inline-block;
    color: var(--accent);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.88rem;
}
.tut-open:hover { text-decoration: underline; }

/* ---- Demo: Example (crossfade) + Test (wipe) ---- */
.tut-demo {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-bottom: 16px;
    max-width: 720px;
}
@media (max-width: 640px) { .tut-demo { grid-template-columns: 1fr; } }

.tut-example, .tut-compare {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 10px;
}
.tut-badge {
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    margin-bottom: 8px;
}
.ex-frame, .cmp-frame {
    position: relative;
    width: 100%;
    aspect-ratio: 1;
    border-radius: var(--radius-sm);
    overflow: hidden;
    background: #111;
}
.ex-frame img, .cmp-frame img {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    image-rendering: pixelated;
    user-select: none;
}
.ex-after { animation: tutCrossfade 5s ease-in-out infinite; }
@keyframes tutCrossfade {
    0%, 38% { opacity: 1; }
    50%, 88% { opacity: 0; }
    100% { opacity: 1; }
}
.ex-cap { text-align: center; font-size: 0.75rem; color: var(--text-secondary); margin-top: 6px; }

/* Wipe slider */
.cmp-frame { cursor: ew-resize; touch-action: none; }
.cmp-after { clip-path: inset(0 calc(100% - var(--pos)) 0 0); }
.cmp-divider {
    position: absolute;
    top: 0; bottom: 0;
    left: var(--pos);
    width: 2px;
    background: var(--accent);
    box-shadow: 0 0 0 1px rgba(0,0,0,0.4);
    pointer-events: none;
}
.cmp-divider::after {
    content: '⇄';
    position: absolute;
    top: 50%; left: 50%;
    transform: translate(-50%, -50%);
    width: 24px; height: 24px;
    background: var(--accent);
    color: #fff;
    border-radius: 50%;
    font-size: 0.8rem;
    display: flex; align-items: center; justify-content: center;
}
.cmp-range { width: 100%; margin-top: 8px; accent-color: var(--accent); cursor: pointer; }
.cmp-foot { display: flex; justify-content: space-between; font-size: 0.75rem; color: var(--text-secondary); margin-top: 2px; }

@media (prefers-reduced-motion: reduce) {
    .ex-after { animation: none; opacity: 0; }
}
@media (max-width: 820px) {
    .tut-layout { grid-template-columns: 1fr; }
    .tut-toc { position: static; max-height: none; }
}

/* ============================================================
   3-column workspace shell: messages (left) · canvas · history (right)
   ============================================================ */
.at-shell {
    display: grid;
    grid-template-columns: 230px minmax(0, 1fr) 270px;
    gap: 16px;
    max-width: 1600px;
    margin: 0 auto;
    padding: 0 16px;
    align-items: start;
}
.at-shell > .app-main { max-width: none; margin: 0; padding: 24px 4px 60px; }
.at-rail {
    position: sticky;
    top: 60px;
    align-self: start;
    max-height: calc(100vh - 76px);
    overflow-y: auto;
    padding: 20px 4px;
}
.at-rail-title {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    font-weight: 700;
    padding: 0 8px 8px;
}

/* Message log (left) */
.at-msg-log { display: flex; flex-direction: column; gap: 6px; }
.at-msg {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-left-width: 3px;
    border-radius: var(--radius-sm);
    padding: 8px 10px;
    font-size: 0.8rem;
    line-height: 1.35;
    color: var(--text-primary);
    opacity: 0;
    transform: translateX(-8px);
    transition: opacity 0.25s ease, transform 0.25s ease;
}
.at-msg.show { opacity: 1; transform: none; }
.at-msg .toast-icon { flex-shrink: 0; }
.at-msg-success { border-left-color: var(--success); }
.at-msg-error   { border-left-color: var(--danger); }
.at-msg-warning { border-left-color: var(--warning); }
.at-msg-info    { border-left-color: var(--info); }

/* History (right) */
.at-hist-list { display: flex; flex-direction: column; gap: 3px; }
.at-hist-item {
    text-align: left;
    background: none;
    border: 1px solid transparent;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 0.8rem;
    padding: 6px 9px;
    cursor: pointer;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    transition: background 0.12s, color 0.12s, border-color 0.12s;
}
.at-hist-item:hover { background: var(--bg-tertiary); color: var(--text-primary); }
.at-hist-item.current {
    background: var(--accent-bg);
    border-color: var(--accent-border);
    color: var(--accent);
    font-weight: 600;
}
.at-hist-item.future { opacity: 0.45; }
.at-hist-item:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }

@media (max-width: 1080px) {
    .at-shell { grid-template-columns: minmax(0, 1fr); }
    .at-shell > .app-main { order: 1; padding: 16px 4px 40px; }
    .at-rail { position: static; max-height: 220px; border-top: 1px solid var(--border); }
    .at-rail-left { order: 3; }
    .at-rail-right { order: 2; }
}