/* ===== DESIGN TOKENS ===== */
:root {
    /* Default surface palette — themes.css overrides these. */
    --surface-0: #0e1020;
    --surface-1: #161830;
    --surface-2: #1c1f3a;
    --surface-3: #232646;
    --surface-glass: rgba(22, 24, 48, 0.72);
    --surface-glass-strong: rgba(14, 16, 32, 0.85);

    --border-subtle: rgba(255, 255, 255, 0.06);
    --border-soft: rgba(255, 255, 255, 0.09);
    --border-strong: rgba(255, 255, 255, 0.16);

    --text-primary: #ecedf7;
    --text-secondary: #b9bcd9;
    --text-muted: #8b8fb3;
    --text-faint: #5e6285;

    --accent: #7c6cff;
    --accent2: #b06bff;
    --accent-soft: rgba(124, 108, 255, 0.16);
    --accent-glow: rgba(124, 108, 255, 0.45);

    --success: #2ecc71;
    --success-soft: rgba(46, 204, 113, 0.14);
    --danger: #ff5c6c;
    --danger-soft: rgba(255, 92, 108, 0.14);
    --warning: #ffb86b;
    --warning-soft: rgba(255, 184, 107, 0.14);

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-xl: 20px;
    --radius-pill: 999px;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.25);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.35);
    --shadow-lg: 0 24px 60px rgba(0, 0, 0, 0.5);
    --shadow-accent: 0 10px 30px rgba(124, 108, 255, 0.28);

    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
    --dur-fast: 120ms;
    --dur-base: 200ms;
    --dur-slow: 360ms;

    --font-sans: 'Inter', 'SF Pro Text', -apple-system, BlinkMacSystemFont, 'Segoe UI Variable', 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'JetBrains Mono', 'SF Mono', 'Cascadia Code', 'Fira Code', Consolas, 'Roboto Mono', monospace;

    color-scheme: dark;
}

/* ===== RESET & BASE ===== */
* { margin: 0; padding: 0; box-sizing: border-box; }
*::selection { background: var(--accent-soft); color: var(--text-primary); }

html, body {
    width: 100%; height: 100%;
    font-family: var(--font-sans);
    font-feature-settings: 'ss01', 'cv11', 'liga';
    font-optical-sizing: auto;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
    overflow: hidden;
    background: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    color: var(--text-primary);
    letter-spacing: -0.005em;
}

/* Ambient wallpaper glow — sits below all chrome */
body::before {
    content: '';
    position: fixed; inset: -10%;
    background:
        radial-gradient(60% 50% at 15% 12%, var(--accent-glow), transparent 60%),
        radial-gradient(45% 45% at 88% 82%, rgba(176, 107, 255, 0.32), transparent 65%);
    opacity: 0.55;
    pointer-events: none;
    z-index: 0;
    filter: blur(20px);
}

/* ===== DESKTOP ===== */
#desktop {
    position: relative; z-index: 1;
    width: 100%; height: 100%;
    display: flex; flex-direction: column;
}
#desktop-icons {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 6px;
    padding: 22px 24px;
    overflow-y: auto;
}
.desktop-section-title {
    font-size: 12px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.14em;
    color: var(--text-secondary);
    text-shadow: 0 1px 4px rgba(0, 0, 0, 0.55);
    padding: 6px 4px 8px;
    border-bottom: 1px solid var(--border-subtle);
    user-select: none;
}
.desktop-section-title:not(:first-child) { margin-top: 18px; }
.desktop-section-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, 104px);
    grid-auto-rows: 116px;
    gap: 14px 10px;
}
.desktop-icon {
    display: flex; flex-direction: column;
    align-items: center; justify-content: flex-start;
    cursor: pointer;
    padding: 10px 6px;
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    transition: background var(--dur-base) var(--ease-out),
                transform var(--dur-base) var(--ease-out),
                border-color var(--dur-base) var(--ease-out),
                box-shadow var(--dur-base) var(--ease-out);
    text-align: center;
    user-select: none;
}
.desktop-icon:hover {
    background: rgba(255, 255, 255, 0.05);
    border-color: var(--border-subtle);
    transform: translateY(-2px);
    box-shadow: 0 12px 28px rgba(0, 0, 0, 0.28);
}
.desktop-icon.selected {
    background: var(--accent-soft);
    border-color: rgba(124, 108, 255, 0.45);
    box-shadow: 0 14px 32px var(--accent-glow);
}
.desktop-icon:active { transform: translateY(-1px) scale(0.98); }
.desktop-icon .icon-emoji {
    font-size: 40px;
    line-height: 1;
    margin-bottom: 8px;
    filter: drop-shadow(0 2px 6px rgba(0, 0, 0, 0.45));
}
.desktop-icon .icon-label {
    font-size: 11.5px;
    font-weight: 500;
    color: var(--text-primary);
    text-shadow: 0 1px 4px rgba(0, 0, 0, 0.55);
    word-break: break-word;
    line-height: 1.25;
    letter-spacing: 0.01em;
}

/* ===== WINDOWS ===== */
#windows-container {
    position: absolute; top: 0; left: 0;
    width: 100%; height: calc(100% - 46px);
    pointer-events: none;
    z-index: 2;
}
.window {
    position: absolute;
    background: var(--surface-glass);
    backdrop-filter: blur(22px) saturate(140%);
    -webkit-backdrop-filter: blur(22px) saturate(140%);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg), inset 0 1px 0 rgba(255, 255, 255, 0.05);
    display: flex; flex-direction: column;
    overflow: hidden;
    pointer-events: auto;
    min-width: 340px; min-height: 260px;
    animation: winPop 0.28s var(--ease-out);
}
@supports not (backdrop-filter: blur(1px)) {
    .window { background: var(--surface-1); }
}
@keyframes winPop {
    from { opacity: 0; transform: scale(0.94) translateY(14px); }
    to   { opacity: 1; transform: scale(1) translateY(0); }
}
.window.active {
    border-color: rgba(124, 108, 255, 0.5);
    box-shadow: var(--shadow-lg), 0 0 0 1px rgba(124, 108, 255, 0.25), 0 30px 70px var(--accent-glow);
}
.window.minimizing { animation: winMinimize 0.22s var(--ease-in-out) forwards; }
.window.maximizing { animation: winMaximize 0.22s var(--ease-out); }
@keyframes winMinimize {
    from { opacity: 1; transform: scale(1); }
    to   { opacity: 0; transform: scale(0.85) translateY(36px); }
}
@keyframes winMaximize {
    from { opacity: 0.85; transform: scale(0.96); }
    to   { opacity: 1; transform: scale(1); }
}
.win-titlebar {
    display: flex; align-items: center;
    padding: 9px 12px 9px 14px;
    background: linear-gradient(180deg, rgba(255,255,255,0.045), rgba(255,255,255,0.012));
    border-bottom: 1px solid var(--border-subtle);
    cursor: grab;
    user-select: none;
}
.win-titlebar:active { cursor: grabbing; }
.win-title {
    flex: 1;
    font-size: 13px; font-weight: 600;
    color: var(--text-primary);
    letter-spacing: 0.005em;
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.win-btns { display: flex; gap: 8px; align-items: center; }
.win-btn {
    width: 13px; height: 13px;
    border-radius: 50%;
    border: 1px solid rgba(0, 0, 0, 0.25);
    cursor: pointer;
    display: flex; align-items: center; justify-content: center;
    font-size: 0; color: transparent;
    transition: filter var(--dur-fast) var(--ease-out),
                transform var(--dur-fast) var(--ease-out);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.25);
    padding: 0;
}
.win-btns:hover .win-btn { font-size: 9px; color: rgba(0, 0, 0, 0.65); font-weight: 700; }
.win-btn:hover { filter: brightness(1.15); transform: scale(1.1); }
.win-min   { background: #f3c14b; }
.win-max   { background: #2fcc6a; }
.win-close { background: #ff6363; }
.win-content {
    flex: 1;
    overflow: auto;
    padding: 18px 20px 22px;
    position: relative;
    background:
        radial-gradient(120% 60% at 50% -10%, rgba(124, 108, 255, 0.08), transparent 60%),
        var(--surface-glass-strong);
}
.win-resize-handle {
    position: absolute; bottom: 0; right: 0;
    width: 16px; height: 16px;
    cursor: se-resize;
    background:
        linear-gradient(135deg, transparent 50%, var(--accent) 50%);
    opacity: 0.55;
    border-bottom-right-radius: var(--radius-lg);
    transition: opacity var(--dur-base) var(--ease-out);
}
.win-resize-handle:hover { opacity: 1; }

/* ===== TASKBAR ===== */
#taskbar {
    height: 46px;
    background: var(--surface-glass-strong);
    backdrop-filter: blur(28px) saturate(160%);
    -webkit-backdrop-filter: blur(28px) saturate(160%);
    border-top: 1px solid var(--border-soft);
    display: flex; align-items: center;
    padding: 0 12px; gap: 10px;
    z-index: 1000;
    box-shadow: 0 -1px 0 rgba(255, 255, 255, 0.03), 0 -10px 30px rgba(0, 0, 0, 0.25);
}
#start-btn {
    padding: 7px 16px;
    background: linear-gradient(135deg, var(--accent), var(--accent2));
    border-radius: var(--radius-sm);
    font-size: 12.5px; font-weight: 600;
    letter-spacing: 0.02em;
    cursor: pointer; user-select: none;
    color: #fff;
    box-shadow: 0 4px 14px var(--accent-glow), inset 0 1px 0 rgba(255, 255, 255, 0.18);
    transition: transform var(--dur-fast) var(--ease-out), box-shadow var(--dur-base) var(--ease-out);
}
#start-btn:hover { transform: translateY(-1px); box-shadow: 0 8px 22px var(--accent-glow), inset 0 1px 0 rgba(255, 255, 255, 0.24); }
#start-btn:active { transform: translateY(0); }
#taskbar-apps {
    flex: 1;
    display: flex; gap: 6px; overflow-x: auto;
    scrollbar-width: thin;
}
.taskbar-app {
    padding: 6px 14px;
    background: rgba(255, 255, 255, 0.045);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-sm);
    font-size: 12px;
    color: var(--text-secondary);
    cursor: pointer; white-space: nowrap;
    border-left: 3px solid var(--accent);
    transition: background var(--dur-base) var(--ease-out),
                color var(--dur-base) var(--ease-out),
                transform var(--dur-fast) var(--ease-out);
}
.taskbar-app:hover { background: rgba(255, 255, 255, 0.09); color: var(--text-primary); transform: translateY(-1px); }
.taskbar-app.inactive { border-left-color: rgba(255, 255, 255, 0.18); opacity: 0.65; }
#clock {
    font-size: 12px;
    font-variant-numeric: tabular-nums;
    color: var(--text-secondary);
    min-width: 56px; text-align: right;
    letter-spacing: 0.03em;
}
#minimize-all,
#lang-btn {
    padding: 0 12px;
    height: 26px;
    cursor: pointer;
    font-size: 12px;
    color: var(--text-muted);
    user-select: none;
    border-left: 1px solid var(--border-subtle);
    display: flex; align-items: center;
    transition: color var(--dur-base) var(--ease-out), background var(--dur-base) var(--ease-out);
    border-radius: 4px;
}
#minimize-all:hover,
#lang-btn:hover { color: var(--text-primary); background: rgba(255, 255, 255, 0.05); }
#lang-btn { font-weight: 600; letter-spacing: 0.06em; }

/* ===== START MENU ===== */
#start-menu {
    position: absolute; bottom: 54px; left: 10px;
    width: 340px; max-height: 540px;
    background: var(--surface-glass-strong);
    backdrop-filter: blur(28px) saturate(160%);
    -webkit-backdrop-filter: blur(28px) saturate(160%);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    display: flex; flex-direction: column;
    z-index: 1001;
    overflow: hidden;
    animation: menuPop 0.22s var(--ease-out);
}
@keyframes menuPop {
    from { opacity: 0; transform: translateY(8px) scale(0.98); }
    to   { opacity: 1; transform: translateY(0) scale(1); }
}
#start-menu.hidden { display: none; }
#start-menu-header {
    padding: 14px 16px;
    background: linear-gradient(135deg, var(--accent), var(--accent2));
    font-size: 14px; font-weight: 700;
    letter-spacing: 0.02em;
    color: #fff;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
}
#start-menu-apps {
    overflow-y: auto; flex: 1;
    padding: 10px 8px;
}
.start-menu-item {
    display: flex; align-items: center;
    gap: 12px; padding: 8px 10px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: background var(--dur-fast) var(--ease-out), transform var(--dur-fast) var(--ease-out);
}
.start-menu-item:hover { background: rgba(255, 255, 255, 0.07); transform: translateX(2px); }
.start-menu-item .smi-emoji { font-size: 20px; }
.start-menu-item .smi-text { font-size: 12.5px; color: var(--text-primary); }
.start-menu-cat {
    font-size: 10.5px; font-weight: 700;
    color: var(--accent2);
    text-transform: uppercase;
    letter-spacing: 0.12em;
    padding: 12px 12px 4px;
    border-top: 1px solid var(--border-subtle);
    margin-top: 6px;
}
.start-menu-cat:first-of-type { border-top: none; margin-top: 0; }

/* ===== APP CONTAINER ===== */
.app-container { max-width: 100%; }
.app-container > * + * { margin-top: 12px; }

/* ----- Typography ----- */
.app-container h2 {
    font-size: 19px;
    font-weight: 700;
    letter-spacing: -0.015em;
    color: var(--text-primary);
    margin-bottom: 14px; padding-bottom: 10px;
    border-bottom: 1px solid var(--border-subtle);
    position: relative;
}
.app-container h2::after {
    content: '';
    position: absolute; left: 0; bottom: -1px;
    width: 56px; height: 2px;
    background: linear-gradient(90deg, var(--accent), var(--accent2));
    border-radius: 2px;
}
.app-container h3 {
    font-size: 14px;
    font-weight: 600;
    letter-spacing: 0.005em;
    color: var(--text-primary);
    margin: 14px 0 8px;
    display: flex; align-items: center; gap: 8px;
}
.app-container h4 {
    font-size: 12.5px; font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin: 10px 0 6px;
}
.app-container p {
    font-size: 13px; line-height: 1.65;
    color: var(--text-secondary);
    margin-bottom: 8px;
}
.app-container p:last-child { margin-bottom: 0; }
.app-container strong, .app-container b { color: var(--text-primary); font-weight: 600; }
.app-container code:not(.katex *) {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background: rgba(255, 255, 255, 0.06);
    border: 1px solid var(--border-subtle);
    border-radius: 4px;
    padding: 1px 6px;
    color: var(--text-primary);
}
.app-container a { color: var(--accent2); text-decoration: none; border-bottom: 1px dashed rgba(176, 107, 255, 0.4); }
.app-container a:hover { border-bottom-style: solid; }

/* ----- Info box ----- */
.app-container .info-box {
    background: var(--accent-soft);
    border: 1px solid rgba(124, 108, 255, 0.22);
    border-left: 3px solid var(--accent);
    padding: 12px 14px;
    border-radius: var(--radius-md);
    font-size: 13px;
    line-height: 1.6;
    color: var(--text-primary);
    margin: 12px 0;
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

/* ----- Formula block ----- */
.app-container .formula {
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.045), rgba(255, 255, 255, 0.015));
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    font-family: var(--font-mono);
    font-size: 14px;
    color: #6df0a4;
    display: inline-block;
    margin: 6px 0;
    border: 1px solid var(--border-subtle);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
    letter-spacing: 0.01em;
}
.app-container .formula-katex {
    font-family: inherit;
    font-size: 15.5px;
    color: var(--text-primary);
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.045), rgba(255, 255, 255, 0.015));
}
.app-container .formula-katex .katex { color: #6df0a4; }
.app-container .formula-katex .katex .text { color: var(--text-muted); font-style: italic; }

/* ----- Buttons ----- */
.app-container button {
    background: linear-gradient(135deg, var(--accent), var(--accent2));
    color: #fff; border: 1px solid transparent;
    padding: 8px 18px;
    border-radius: var(--radius-sm);
    font-size: 12.5px; font-weight: 600;
    font-family: inherit;
    letter-spacing: 0.01em;
    cursor: pointer;
    transition: transform var(--dur-fast) var(--ease-out),
                box-shadow var(--dur-base) var(--ease-out),
                filter var(--dur-fast) var(--ease-out);
    margin: 4px 4px 4px 0;
    box-shadow: 0 4px 14px var(--accent-glow), inset 0 1px 0 rgba(255, 255, 255, 0.16);
}
.app-container button:hover { transform: translateY(-1px); box-shadow: 0 8px 22px var(--accent-glow), inset 0 1px 0 rgba(255, 255, 255, 0.22); filter: brightness(1.04); }
.app-container button:active { transform: translateY(0); filter: brightness(0.95); }
.app-container button:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}
.app-container button:disabled {
    opacity: 0.5; cursor: not-allowed; transform: none;
    box-shadow: none; filter: grayscale(0.4);
}

/* ----- Form controls ----- */
.app-container input[type="range"] {
    -webkit-appearance: none; appearance: none;
    width: 100%; height: 22px;
    margin: 6px 0;
    background: transparent;
    cursor: pointer;
}
.app-container input[type="range"]::-webkit-slider-runnable-track {
    height: 5px;
    background: linear-gradient(90deg, rgba(124, 108, 255, 0.55), rgba(176, 107, 255, 0.35));
    border-radius: var(--radius-pill);
    border: 1px solid var(--border-subtle);
}
.app-container input[type="range"]::-moz-range-track {
    height: 5px;
    background: linear-gradient(90deg, rgba(124, 108, 255, 0.55), rgba(176, 107, 255, 0.35));
    border-radius: var(--radius-pill);
    border: 1px solid var(--border-subtle);
}
.app-container input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 16px; height: 16px;
    border-radius: 50%;
    background: #fff;
    border: 2px solid var(--accent);
    margin-top: -7px;
    box-shadow: 0 2px 8px var(--accent-glow);
    transition: transform var(--dur-fast) var(--ease-out);
}
.app-container input[type="range"]::-moz-range-thumb {
    width: 16px; height: 16px;
    border-radius: 50%;
    background: #fff;
    border: 2px solid var(--accent);
    box-shadow: 0 2px 8px var(--accent-glow);
}
.app-container input[type="range"]:hover::-webkit-slider-thumb { transform: scale(1.12); }
.app-container input[type="range"]:focus-visible { outline: none; }
.app-container input[type="range"]:focus-visible::-webkit-slider-thumb {
    box-shadow: 0 0 0 4px var(--accent-soft), 0 2px 8px var(--accent-glow);
}

.app-container input[type="number"],
.app-container input[type="text"],
.app-container input[type="search"],
.app-container input[type="email"],
.app-container select,
.app-container textarea {
    background: rgba(0, 0, 0, 0.28);
    border: 1px solid var(--border-soft);
    color: var(--text-primary);
    padding: 6px 10px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-family: inherit;
    transition: border-color var(--dur-base) var(--ease-out), box-shadow var(--dur-base) var(--ease-out);
    outline: none;
}
.app-container input:focus,
.app-container select:focus,
.app-container textarea:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-soft);
}
.app-container select {
    appearance: none; -webkit-appearance: none;
    padding-right: 28px;
    background-image: linear-gradient(45deg, transparent 50%, var(--text-muted) 50%),
                      linear-gradient(135deg, var(--text-muted) 50%, transparent 50%);
    background-position: calc(100% - 14px) 50%, calc(100% - 9px) 50%;
    background-size: 5px 5px, 5px 5px;
    background-repeat: no-repeat;
}
.app-container input[type="checkbox"],
.app-container input[type="radio"] {
    accent-color: var(--accent);
    width: 14px; height: 14px;
    cursor: pointer;
    vertical-align: -2px;
    margin-right: 6px;
}

/* ----- Canvas ----- */
.app-container canvas {
    background:
        radial-gradient(140% 80% at 50% 0%, rgba(124, 108, 255, 0.06), transparent 60%),
        #07091a;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-subtle);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.03), 0 6px 20px rgba(0, 0, 0, 0.25);
    display: block; margin: 12px 0;
    max-width: 100%;
}

/* ----- Control row ----- */
.app-container .control-row {
    display: flex; align-items: center;
    gap: 12px; margin: 10px 0;
    flex-wrap: wrap;
    padding: 8px 12px;
    background: rgba(255, 255, 255, 0.025);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
}
.app-container .control-row > label {
    font-size: 12px; color: var(--text-secondary);
    min-width: 100px;
    font-weight: 500;
    display: flex; align-items: center; gap: 6px;
}
.app-container .control-row > label > span {
    color: var(--text-primary);
    font-weight: 600;
    font-variant-numeric: tabular-nums;
}

/* ----- Layout ----- */
.app-container .grid-2 {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
}
@media (max-width: 640px) {
    .app-container .grid-2 { grid-template-columns: 1fr; }
}
.app-container .card {
    background:
        linear-gradient(180deg, rgba(255, 255, 255, 0.045), rgba(255, 255, 255, 0.012));
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    padding: 16px 18px;
    box-shadow: var(--shadow-sm), inset 0 1px 0 rgba(255, 255, 255, 0.035);
    transition: border-color var(--dur-base) var(--ease-out), box-shadow var(--dur-base) var(--ease-out);
}
.app-container .card:hover {
    border-color: var(--border-strong);
    box-shadow: var(--shadow-md), inset 0 1px 0 rgba(255, 255, 255, 0.05);
}

/* ----- Tables ----- */
.app-container table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    font-size: 12.5px;
    margin: 12px 0;
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    overflow: hidden;
}
.app-container th,
.app-container td {
    padding: 9px 12px; text-align: left;
    border-bottom: 1px solid var(--border-subtle);
}
.app-container tr:last-child td { border-bottom: none; }
.app-container th {
    background: rgba(124, 108, 255, 0.12);
    color: var(--text-primary);
    font-weight: 600;
    font-size: 11.5px;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    border-bottom-color: var(--border-soft);
}
.app-container tbody tr:nth-child(even) td { background: rgba(255, 255, 255, 0.015); }
.app-container tbody tr:hover td { background: rgba(124, 108, 255, 0.06); }

/* ===== SHARED HELPERS (tabs / related / formula typography) ===== */
.sd-tabs { margin: 12px 0; }
.sd-tabbar {
    display: flex; gap: 4px;
    border-bottom: 1px solid var(--border-subtle);
    flex-wrap: wrap;
    padding-bottom: 0;
}
.sd-tab {
    background: rgba(255, 255, 255, 0.03) !important;
    color: var(--text-secondary) !important;
    padding: 7px 14px !important;
    border-radius: var(--radius-sm) var(--radius-sm) 0 0 !important;
    margin: 0 !important;
    font-size: 12px !important;
    font-weight: 500 !important;
    border: 1px solid var(--border-subtle) !important;
    border-bottom: none !important;
    box-shadow: none !important;
    transition: background var(--dur-fast) var(--ease-out), color var(--dur-fast) var(--ease-out) !important;
    transform: none !important;
}
.sd-tab:hover { background: rgba(255, 255, 255, 0.06) !important; color: var(--text-primary) !important; transform: none !important; }
.sd-tab.active {
    background: linear-gradient(135deg, var(--accent, #7c6cff), var(--accent2, #b06bff)) !important;
    color: #fff !important;
    border-color: transparent !important;
    box-shadow: 0 -2px 10px var(--accent-glow) !important;
}
.sd-tabpanel { padding: 14px 4px 8px; }

.sd-related {
    margin-top: 16px; padding: 12px 14px;
    background: rgba(255, 255, 255, 0.025);
    border: 1px dashed var(--border-soft);
    border-radius: var(--radius-md);
    display: flex; align-items: center; flex-wrap: wrap; gap: 8px;
}
.sd-related-label {
    font-size: 10.5px; color: var(--text-muted);
    text-transform: uppercase; letter-spacing: 0.1em;
    margin-right: 4px;
    font-weight: 600;
}
.sd-related-link {
    background: rgba(124, 108, 255, 0.12) !important;
    border: 1px solid rgba(124, 108, 255, 0.3) !important;
    color: var(--text-primary) !important;
    padding: 5px 12px !important;
    border-radius: var(--radius-pill) !important;
    margin: 0 !important;
    font-size: 11.5px !important;
    font-weight: 500 !important;
    box-shadow: none !important;
    transition: background var(--dur-base) var(--ease-out), transform var(--dur-fast) var(--ease-out) !important;
}
.sd-related-link:hover {
    background: rgba(124, 108, 255, 0.25) !important;
    transform: translateY(-1px) !important;
    box-shadow: 0 4px 12px var(--accent-glow) !important;
}

/* Formula typography helpers */
.frac { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; font-size: 0.9em; }
.frac > .num { border-bottom: 1px solid currentColor; padding: 0 4px; }
.frac > .den { padding: 0 4px; }
.vec { position: relative; }
.vec::after { content: '⃗'; font-size: 0.8em; }
.app-container .formula sup,
.app-container .formula sub { font-size: 0.7em; }

/* Section anchors used by appShell */
.sd-section { margin-top: 14px; }
.sd-section + .sd-section { margin-top: 16px; }

/* ===== SCROLLBARS ===== */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-pill);
    border: 2px solid transparent;
    background-clip: padding-box;
}
::-webkit-scrollbar-thumb:hover { background-color: rgba(255, 255, 255, 0.18); }
::-webkit-scrollbar-corner { background: transparent; }

* { scrollbar-width: thin; scrollbar-color: rgba(255, 255, 255, 0.12) transparent; }

/* ===== BUTTON VARIANTS ===== */
.app-container button.btn-danger {
    background: linear-gradient(135deg, var(--danger), #d94e6b) !important;
    box-shadow: 0 4px 14px rgba(255, 92, 108, 0.32), inset 0 1px 0 rgba(255, 255, 255, 0.18);
}
.app-container button.btn-danger:hover {
    box-shadow: 0 8px 22px rgba(255, 92, 108, 0.42), inset 0 1px 0 rgba(255, 255, 255, 0.24);
}
.app-container button.btn-ghost {
    background: transparent !important;
    color: var(--text-secondary) !important;
    border: 1px solid var(--border-soft) !important;
    box-shadow: none !important;
}
.app-container button.btn-ghost:hover {
    background: rgba(255, 255, 255, 0.05) !important;
    color: var(--text-primary) !important;
    border-color: var(--border-strong) !important;
}
.app-container button.btn-secondary {
    background: rgba(255, 255, 255, 0.06) !important;
    color: var(--text-primary) !important;
    border: 1px solid var(--border-soft) !important;
    box-shadow: none !important;
}
.app-container button.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.1) !important;
    border-color: var(--border-strong) !important;
}

/* ===== TL;DR + REAL-WORLD CALLOUTS ===== */
.sd-tldr {
    display: flex; align-items: flex-start; gap: 10px;
    padding: 10px 14px;
    margin: 4px 0 14px;
    background:
        linear-gradient(135deg, var(--accent-soft), rgba(255, 255, 255, 0.025));
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-md);
    box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
    font-size: 13px;
    line-height: 1.55;
    color: var(--text-primary);
}
.sd-tldr-tag {
    flex-shrink: 0;
    font-size: 10px;
    font-weight: 700;
    letter-spacing: 0.14em;
    color: var(--accent2);
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid var(--border-subtle);
    padding: 3px 8px;
    border-radius: var(--radius-pill);
    text-transform: uppercase;
    align-self: center;
}
.sd-tldr-text { flex: 1; }
.app-container .info-box.sd-real-world {
    background:
        linear-gradient(135deg, rgba(46, 204, 113, 0.1), rgba(255, 255, 255, 0.015));
    border-color: rgba(46, 204, 113, 0.28);
    border-left-color: var(--success);
}

/* ===== REDUCED MOTION ===== */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
    body::before { animation: none !important; }
}

/* ===== CONTEXT MENU (dynamic, styled inline by desktop.js) ===== */
/* Selector preserved for future polish if desktop.js stops inlining styles. */