/* ===== CSS Variables - NEO Education Theme (Dynamic Color Mixing) ===== */
:root {
    /* Core Base Colors (Dark Mode Default) */
    --base-dark: #0a0f1a;
    --base-card: #111827;

    /* Dynamic Backgrounds with Color Mixing (Material You Style) */
    /* Mix 5-10% of Accent into the base dark colors */
    --bg-primary: color-mix(in srgb, var(--accent) 5%, var(--base-dark));
    --bg-secondary: color-mix(in srgb, var(--accent) 8%, #111827);
    --bg-card: color-mix(in srgb, var(--accent) 5%, rgba(17, 24, 39, 0.95));
    --bg-card-solid: color-mix(in srgb, var(--accent) 5%, #1a1f2e);
    --bg-hover: color-mix(in srgb, var(--accent) 10%, rgba(30, 41, 59, 0.8));

    /* Apple-style Glass (Tinted) */
    --glass-material: color-mix(in srgb, var(--accent) 5%, rgba(30, 30, 40, 0.65));
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.3);
    --glass-blur: blur(20px) saturate(180%);

    /* Context Colors */
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    /* Accents - Default Purple */
    --accent: #7c3aed;
    --accent-hover: #9c7eff;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, var(--accent), var(--accent-secondary));

    /* Additional Mappings */
    --accent-secondary: #2dd4bf;
    --accent-tertiary: #a855f7;

    /* Functional Colors */
    --correct: #34d399;
    /* Soft Emerald */
    --correct-bg: rgba(52, 211, 153, 0.15);
    --incorrect: #f87171;
    /* Soft Red */
    --incorrect-bg: rgba(248, 113, 113, 0.15);
    --warning: #fbbf24;
    /* Soft Amber */
    --warning-bg: rgba(251, 191, 36, 0.15);

    /* Borders & Shadows */
    --border: var(--md-outline-variant);
    --border-strong: var(--md-outline);
    --shadow: var(--md-shadow-3);
    --shadow-sm: var(--md-shadow-1);
    --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.5);

    /* Spacing & Radius */
    --radius: 24px;
    /* More rounded for Apple/M3 feel */
    --radius-sm: 12px;
    --radius-xs: 8px;
    --radius-full: 9999px;

    /* Transitions */
    --transition: all 0.4s cubic-bezier(0.25, 1, 0.5, 1);
    /* Soft Spring-like */
    --transition-fast: all 0.15s ease;

    /* Typography */
    --font: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Segoe UI", Roboto, sans-serif;

    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;
}

/* Light Mode */
[data-theme="light"] {
    /* Light theme follows M3 surfaces with a subtle Material You tint */
    /* Background should not be pure white; cards slightly darker for hierarchy */
    --bg-primary: var(--md-surface-container-low);
    --bg-secondary: var(--md-surface);
    --bg-card: var(--md-surface-container);
    --bg-card-solid: var(--md-surface-container-high);
    --bg-hover: var(--md-surface-container-highest);

    --bg-glass: color-mix(in srgb, var(--accent) 6%, color-mix(in srgb, var(--md-surface-container) 86%, transparent));
    --glass-material: color-mix(in srgb, var(--accent) 8%, var(--md-surface-container));
    --glass-border: var(--md-outline-variant);
    --glass-shadow: var(--md-shadow-1);
    --glass-blur: blur(14px) saturate(130%);

    --text-primary: var(--md-on-surface);
    --text-secondary: var(--md-on-surface-variant);
    --text-muted: color-mix(in srgb, var(--md-on-surface) 55%, transparent);
    --border: var(--md-outline-variant);
    --border-strong: var(--md-outline);
    --shadow: var(--md-shadow-2);
    --shadow-sm: var(--md-shadow-1);
    --shadow-lg: var(--md-shadow-2);
}

/* ===== Experimental Color Themes ===== */

/* Ocean Theme (Blue/Teal) */
html[data-color-theme="ocean"] {
    --accent: #0ea5e9;
    --accent-hover: #38bdf8;
    --accent-light: rgba(14, 165, 233, 0.15);
    --accent-gradient: linear-gradient(135deg, #0ea5e9, #2dd4bf);
    --accent-secondary: #2dd4bf;
    --accent-tertiary: #6366f1;
}

/* Nature Theme (Green/Lime) */
html[data-color-theme="nature"] {
    --accent: #10b981;
    --accent-hover: #34d399;
    --accent-light: rgba(16, 185, 129, 0.15);
    --accent-gradient: linear-gradient(135deg, #10b981, #84cc16);
    --accent-secondary: #84cc16;
    --accent-tertiary: #06b6d4;
}

/* Sunset Theme (Orange/Red) */
html[data-color-theme="sunset"] {
    --accent: #f59e0b;
    --accent-hover: #fbbf24;
    --accent-light: rgba(245, 158, 11, 0.15);
    --accent-gradient: linear-gradient(135deg, #f59e0b, #ef4444);
    --accent-secondary: #ef4444;
    --accent-tertiary: #d946ef;
}

/* Berry Theme (Pink/Rose) */
html[data-color-theme="berry"] {
    --accent: #ec4899;
    --accent-hover: #f472b6;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #ec4899, #f43f5e);
    --accent-secondary: #f43f5e;
    --accent-tertiary: #8b5cf6;
}

/* Royal Theme (Indigo/Gold) */
html[data-color-theme="royal"] {
    --accent: #4338ca;
    /* Indigo 700 */
    --accent-hover: #6366f1;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #4338ca, #eab308);
    /* Indigo to Gold */
    --accent-secondary: #eab308;
    --accent-tertiary: #a855f7;
}

/* Midnight Theme (Slate/Blue) */
html[data-color-theme="midnight"] {
    --accent: #334155;
    /* Slate 700 */
    --accent-hover: #475569;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #0f172a, #3b82f6);
    /* Dark Slate to Blue */
    --accent-secondary: #3b82f6;
    --accent-tertiary: #64748b;
}

/* Coffee Theme (Brown/Amber) */
html[data-color-theme="coffee"] {
    --accent: #78350f;
    /* Amber 900 */
    --accent-hover: #92400e;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #78350f, #d97706);
    /* Brown to Amber */
    --accent-secondary: #d97706;
    --accent-tertiary: #a16207;
}

/* Crimson Theme (Red/Rose) */
html[data-color-theme="crimson"] {
    --accent: #9f1239;
    /* Rose 800 */
    --accent-hover: #be123c;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #9f1239, #f43f5e);
    /* Deep Rose to Pink */
    --accent-secondary: #f43f5e;
    --accent-tertiary: #881337;
}

/* Teal Theme (Teal/Cyan) */
html[data-color-theme="teal"] {
    --accent: #0d9488;
    --accent-hover: #14b8a6;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #0d9488, #22d3ee);
    --accent-secondary: #22d3ee;
    --accent-tertiary: #115e59;
}

/* ===== NEW COLOR THEMES ===== */

/* Rose Theme */
html[data-color-theme="rose"] {
    --accent: #f43f5e;
    --accent-hover: #fb7185;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #f43f5e, #ec4899);
    --accent-secondary: #ec4899;
    --accent-tertiary: #e11d48;
}

/* Coral Theme */
html[data-color-theme="coral"] {
    --accent: #fb7185;
    --accent-hover: #fda4af;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #fb7185, #f43f5e);
    --accent-secondary: #f43f5e;
    --accent-tertiary: #fda4af;
}

/* Orange Theme */
html[data-color-theme="orange"] {
    --accent: #f97316;
    --accent-hover: #fb923c;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #f97316, #f59e0b);
    --accent-secondary: #f59e0b;
    --accent-tertiary: #ea580c;
}

/* Peach Theme */
html[data-color-theme="peach"] {
    --accent: #fdba74;
    --accent-hover: #fed7aa;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #fdba74, #fb923c);
    --accent-secondary: #fb923c;
    --accent-tertiary: #fed7aa;
}

/* Cyan Theme */
html[data-color-theme="cyan"] {
    --accent: #06b6d4;
    --accent-hover: #22d3ee;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #06b6d4, #0ea5e9);
    --accent-secondary: #0ea5e9;
    --accent-tertiary: #0891b2;
}

/* Sky Theme */
html[data-color-theme="sky"] {
    --accent: #38bdf8;
    --accent-hover: #7dd3fc;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #38bdf8, #0ea5e9);
    --accent-secondary: #0ea5e9;
    --accent-tertiary: #0284c7;
}

/* Indigo Theme */
html[data-color-theme="indigo"] {
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #6366f1, #8b5cf6);
    --accent-secondary: #8b5cf6;
    --accent-tertiary: #4f46e5;
}

/* Violet Theme */
html[data-color-theme="violet"] {
    --accent: #8b5cf6;
    --accent-hover: #a78bfa;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #8b5cf6, #a855f7);
    --accent-secondary: #a855f7;
    --accent-tertiary: #7c3aed;
}

/* Purple Theme */
html[data-color-theme="purple"] {
    --accent: #a855f7;
    --accent-hover: #c084fc;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #a855f7, #d946ef);
    --accent-secondary: #d946ef;
    --accent-tertiary: #9333ea;
}

/* Amber Theme */
html[data-color-theme="amber"] {
    --accent: #d97706;
    --accent-hover: #f59e0b;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #d97706, #fbbf24);
    --accent-secondary: #fbbf24;
    --accent-tertiary: #b45309;
}

/* Olive Theme */
html[data-color-theme="olive"] {
    --accent: #65a30d;
    --accent-hover: #84cc16;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #65a30d, #a3e635);
    --accent-secondary: #a3e635;
    --accent-tertiary: #4d7c0f;
}

/* Emerald Theme */
html[data-color-theme="emerald"] {
    --accent: #059669;
    --accent-hover: #10b981;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #059669, #34d399);
    --accent-secondary: #34d399;
    --accent-tertiary: #047857;
}

/* Slate Theme */
html[data-color-theme="slate"] {
    --accent: #475569;
    --accent-hover: #64748b;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #475569, #94a3b8);
    --accent-secondary: #94a3b8;
    --accent-tertiary: #334155;
}

/* ===== GRADIENT THEMES ===== */

/* Aurora Theme (Cyan to Violet) */
html[data-color-theme="aurora"] {
    --accent: #06b6d4;
    --accent-hover: #22d3ee;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #06b6d4, #8b5cf6);
    --accent-secondary: #8b5cf6;
    --accent-tertiary: #0891b2;
}

/* Sakura Theme (Pink to Rose) */
html[data-color-theme="sakura"] {
    --accent: #f472b6;
    --accent-hover: #f9a8d4;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #f472b6, #fb7185);
    --accent-secondary: #fb7185;
    --accent-tertiary: #ec4899;
}

/* Forest Theme (Emerald to Lime) */
html[data-color-theme="forest"] {
    --accent: #059669;
    --accent-hover: #10b981;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #059669, #84cc16);
    --accent-secondary: #84cc16;
    --accent-tertiary: #047857;
}

/* Fire Theme (Amber to Red) */
html[data-color-theme="fire"] {
    --accent: #f59e0b;
    --accent-hover: #fbbf24;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #f59e0b, #dc2626);
    --accent-secondary: #dc2626;
    --accent-tertiary: #d97706;
}

/* Galaxy Theme (Indigo to Pink) */
html[data-color-theme="galaxy"] {
    --accent: #4338ca;
    --accent-hover: #6366f1;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #4338ca, #ec4899);
    --accent-secondary: #ec4899;
    --accent-tertiary: #3730a3;
}

/* Mint Theme (Green to Cyan) */
html[data-color-theme="mint"] {
    --accent: #10b981;
    --accent-hover: #34d399;
    --accent-light: color-mix(in srgb, var(--accent) 15%, transparent);
    --accent-gradient: linear-gradient(135deg, #10b981, #06b6d4);
    --accent-secondary: #06b6d4;
    --accent-tertiary: #059669;
}

/* ===== Reset & Base ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: var(--font);
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.7;
    font-size: 16px;
    overflow-x: hidden;
}

/* Container with responsive widths */
.container {
    width: 100%;
    max-width: 1000px;
    margin: 0 auto;
    padding: var(--space-lg);
}

.container-wide {
    max-width: 1200px;
}

.hidden {
    display: none !important;
}

/* ===== Main Header - Material Design 3 ===== */
.main-header {
    position: sticky;
    top: 0;
    z-index: 90;
    /* Below Nav which is 1000 */
    background: transparent;
    /* Cleaner, let content scroll behind? Or blurred? */
    /* Let's use blurred surface for readability but cleaner border */
    background: rgba(var(--md-surface-rgb), 0.7);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    /* Remove harsh border */
    transition: background 0.3s, box-shadow 0.3s;
}

/* Add shadow on scroll via JS? Or just keep simple. */
.main-header.scrolled {
    background: rgba(var(--md-surface-rgb), 0.95);
    box-shadow: var(--md-shadow-1);
    border-bottom: 1px solid var(--md-outline-variant);
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 12px var(--space-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    /* Center the logo */
    gap: var(--space-md);
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    white-space: nowrap;
    text-decoration: none;
    transition: var(--transition);
}

/* Centered logo style for simplified header */
.header-logo-centered {
    font-size: 1.1rem;
    text-align: center;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

/* Logo image theme switching */
.logo-img {
    height: 32px;
    width: auto;
    display: none;
}

/* Logo text styling */
.logo-text {
    font-size: 1.1rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Dark theme: show dark_logo (visible on dark background) */
[data-theme="dark"] .logo-for-dark {
    display: block;
}

/* Light theme: show white_logo (visible on light background) */
[data-theme="light"] .logo-for-light {
    display: block;
}

/* Default (dark theme): show dark logo */
.logo-for-dark {
    display: block;
}

[data-theme="light"] .logo-for-dark {
    display: none;
}

.logo:hover {
    transform: scale(1.02);
}

/* Navigation Links - M3 Navigation Bar */
/* Navigation - Universal Bottom Dock with Liquid Glass Effect */
.main-nav {
    display: flex;
    gap: 8px;
    /* Liquid Glass: semi-transparent with strong blur */
    background: linear-gradient(135deg,
            rgba(30, 35, 50, 0.65) 0%,
            rgba(45, 50, 70, 0.55) 50%,
            rgba(30, 35, 50, 0.65) 100%);
    padding: 10px 16px;
    border-radius: 99px;
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 1000;
    /* Multi-layer shadow for depth */
    box-shadow:
        0 8px 32px rgba(0, 0, 0, 0.3),
        0 2px 8px rgba(0, 0, 0, 0.2),
        inset 0 1px 1px rgba(255, 255, 255, 0.08);
    /* Strong blur for liquid glass */
    backdrop-filter: blur(24px) saturate(1.5);
    -webkit-backdrop-filter: blur(24px) saturate(1.5);
    /* Subtle luminous border */
    border: 1px solid rgba(255, 255, 255, 0.15);
    transition: all 0.3s cubic-bezier(0.2, 0, 0, 1);
}

/* Liquid glass hover glow */
.main-nav:hover {
    box-shadow:
        0 8px 40px rgba(124, 58, 237, 0.15),
        0 4px 16px rgba(0, 0, 0, 0.25),
        inset 0 1px 1px rgba(255, 255, 255, 0.1);
    border-color: rgba(255, 255, 255, 0.2);
}

/* Light mode - Frosted glass look */
[data-theme="light"] .main-nav {
    background: linear-gradient(135deg,
            rgba(255, 255, 255, 0.7) 0%,
            rgba(248, 250, 255, 0.6) 50%,
            rgba(255, 255, 255, 0.7) 100%);
    box-shadow:
        0 8px 32px rgba(0, 0, 0, 0.08),
        0 2px 8px rgba(0, 0, 0, 0.05),
        inset 0 1px 2px rgba(255, 255, 255, 0.9);
    border: 1px solid rgba(255, 255, 255, 0.6);
}

[data-theme="light"] .main-nav:hover {
    box-shadow:
        0 8px 40px rgba(124, 58, 237, 0.1),
        0 4px 16px rgba(0, 0, 0, 0.06),
        inset 0 1px 2px rgba(255, 255, 255, 0.9);
    border-color: rgba(255, 255, 255, 0.8);
}

.nav-tab {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 20px;
    border: none;
    background: transparent;
    /* Ensure text is visible on glass background */
    color: rgba(255, 255, 255, 0.85);
    font-size: 14px;
    font-weight: 500;
    font-family: var(--md-font);
    cursor: pointer;
    border-radius: var(--md-shape-full);
    transition: all var(--md-motion-duration-medium) var(--md-motion-easing-standard);
    text-decoration: none;
    white-space: nowrap;
    position: relative;
    overflow: hidden;
}

/* Light mode text color */
[data-theme="light"] .nav-tab {
    color: rgba(30, 41, 59, 0.85);
}

/* Hover state - subtle glass highlight */
.nav-tab:hover {
    background: rgba(255, 255, 255, 0.12);
    color: #ffffff;
    transform: translateY(-1px);
}

[data-theme="light"] .nav-tab:hover {
    background: rgba(0, 0, 0, 0.06);
    color: #0f172a;
}

/* Active state - Liquid Glass Pill Effect */
.nav-tab.active {
    background: linear-gradient(135deg,
            rgba(124, 58, 237, 0.35) 0%,
            rgba(6, 182, 212, 0.25) 100%);
    color: #ffffff;
    box-shadow:
        0 2px 8px rgba(124, 58, 237, 0.25),
        inset 0 1px 1px rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.15);
}

[data-theme="light"] .nav-tab.active {
    background: linear-gradient(135deg,
            rgba(124, 58, 237, 0.25) 0%,
            rgba(6, 182, 212, 0.15) 100%);
    color: #4c1d95;
    box-shadow:
        0 2px 8px rgba(124, 58, 237, 0.15),
        inset 0 1px 1px rgba(255, 255, 255, 0.5);
    border: 1px solid rgba(124, 58, 237, 0.2);
}

.tab-icon {
    font-size: 1.1rem;
}

/* Mobile Menu Toggle */
.menu-toggle {
    display: none;
    width: 44px;
    height: 44px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--bg-card);
    cursor: pointer;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    transition: var(--transition);
}

.menu-toggle:hover {
    border-color: var(--accent);
    background: var(--accent-light);
}

.theme-toggle {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    border: 1px solid var(--border);
    background: var(--bg-card);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    transition: var(--transition);
    flex-shrink: 0;
}

.theme-toggle:hover {
    transform: rotate(20deg) scale(1.05);
    border-color: var(--accent);
}

/* ===== Main Content ===== */
.main-content {
    min-height: calc(100vh - 70px);
    padding-bottom: 120px;
    /* Space for Bottom Nav */
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {

    0%,
    100% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.05);
    }
}

/* ===== Card Components ===== */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: var(--space-lg);
    transition: var(--transition);
}

.card:hover {
    border-color: var(--accent);
    box-shadow: var(--shadow-sm);
}

.card-glass {
    background: var(--bg-glass);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

/* ===== Common Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 20px;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    font-family: var(--font);
    cursor: pointer;
    transition: var(--transition);
    text-decoration: none;
    white-space: nowrap;
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background: var(--accent-gradient);
    color: white;
    box-shadow: 0 4px 15px rgba(124, 58, 237, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(124, 58, 237, 0.4);
}

.btn-secondary {
    background: var(--bg-card);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

.btn-secondary:hover {
    border-color: var(--accent);
    background: var(--accent-light);
}

.btn-success {
    background: var(--correct);
    color: white;
}

.btn-danger {
    background: var(--incorrect);
    color: white;
}

.btn-warning {
    background: linear-gradient(135deg, #f59e0b, #f97316);
    color: white;
}

.btn-lg {
    padding: 16px 32px;
    font-size: 1.05rem;
    border-radius: var(--radius);
}

.btn-sm {
    padding: 8px 14px;
    font-size: 0.85rem;
}

.btn-block {
    width: 100%;
}

.btn-icon {
    width: 44px;
    height: 44px;
    padding: 0;
    border-radius: 50%;
}

/* Legacy button support */
.action-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 20px;
    background: var(--bg-card);
    color: var(--text-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    font-family: var(--font);
    cursor: pointer;
    transition: var(--transition);
}

.action-btn:hover {
    border-color: var(--accent);
    background: var(--accent-light);
}

.action-btn.primary {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

.action-btn.primary:hover {
    background: var(--accent-hover);
}

.action-btn-large {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    padding: 18px 36px;
    background: var(--accent-gradient);
    color: white;
    border: none;
    border-radius: var(--radius);
    font-size: 1.1rem;
    font-weight: 600;
    font-family: var(--font);
    cursor: pointer;
    transition: var(--transition);
    box-shadow: 0 4px 20px rgba(124, 58, 237, 0.4);
    text-decoration: none;
}

.action-btn-large:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 30px rgba(124, 58, 237, 0.5);
}

/* ===== Badge Components ===== */
.badge {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 4px 10px;
    border-radius: var(--radius-full);
    font-size: 0.75rem;
    font-weight: 600;
}

.badge-primary {
    background: var(--accent-light);
    color: var(--accent);
}

.badge-success {
    background: var(--correct-bg);
    color: var(--correct);
}

.badge-warning {
    background: var(--warning-bg);
    color: var(--warning);
}

.badge-gradient {
    background: var(--accent-gradient);
    color: white;
}

/* ===== Form Elements ===== */
.form-group {
    margin-bottom: var(--space-md);
}

.form-label {
    display: block;
    margin-bottom: var(--space-xs);
    font-weight: 500;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.form-input,
.form-select {
    width: 100%;
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-primary);
    font-family: var(--font);
    font-size: 0.95rem;
    transition: var(--transition);
}

.form-input:focus,
.form-select:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-light);
}

select {
    padding: 10px 16px;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--bg-card);
    color: var(--text-primary);
    font-family: var(--font);
    font-size: 0.95rem;
    cursor: pointer;
}

.toggle-inline {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.toggle-inline input[type="checkbox"] {
    width: 18px;
    height: 18px;
    accent-color: var(--accent);
}

/* ===== Quiz Options ===== */
.options {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-top: 20px;
}

.option {
    display: flex;
    align-items: flex-start;
    gap: 14px;
    padding: 16px 20px;
    background: var(--bg-secondary);
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    position: relative;
}

.option:hover:not(.disabled) {
    border-color: var(--accent);
    background: var(--accent-light);
    transform: translateX(4px);
}

.option.correct {
    border-color: var(--correct);
    background: var(--correct-bg);
}

.option.incorrect {
    border-color: var(--incorrect);
    background: var(--incorrect-bg);
}

.option.selected {
    border-color: var(--accent);
    background: var(--accent-light);
}

.option.disabled {
    cursor: default;
    pointer-events: none;
}

.option-letter {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-light);
    color: var(--accent);
    border-radius: 50%;
    font-weight: 700;
    font-size: 0.9rem;
    flex-shrink: 0;
}

.option.correct .option-letter {
    background: var(--correct);
    color: white;
}

.option.incorrect .option-letter {
    background: var(--incorrect);
    color: white;
}

.option-text {
    flex: 1;
    line-height: 1.6;
    padding-top: 4px;
}

.option-icon {
    position: absolute;
    right: 16px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 1.3rem;
}

/* ===== Progress Bar ===== */
.progress-bar {
    height: 6px;
    background: var(--bg-secondary);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent-gradient);
    border-radius: 3px;
    transition: width 0.3s ease;
}

/* ===== Explanation Box ===== */
.explanation-box {
    margin-top: 20px;
    background: linear-gradient(135deg, rgba(124, 58, 237, 0.05), rgba(6, 182, 212, 0.05));
    border: 1px solid var(--accent);
    border-radius: var(--radius);
    padding: 20px;
    animation: slideUp 0.5s ease;
    border-left: 4px solid var(--accent);
}

.explanation-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
}

.gemini-badge {
    background: linear-gradient(90deg, #4285f4, #8b5cf6);
    color: white;
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
}

.explanation-text {
    color: var(--text-primary);
    line-height: 1.8;
    font-size: 0.95rem;
}

/* ===== Modal ===== */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1000;
}

.modal.active {
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
}

.modal-content {
    position: relative;
    background: var(--bg-card-solid);
    border-radius: var(--radius);
    padding: 40px;
    max-width: 450px;
    width: 90%;
    text-align: center;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border);
    animation: modalIn 0.3s ease;
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: scale(0.9) translateY(20px);
    }

    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}

.result-emoji {
    font-size: 4rem;
    margin-bottom: 16px;
    animation: pulse 1s ease infinite;
}

.result-score {
    font-size: 3rem;
    font-weight: 800;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 12px;
}

.result-detail {
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.result-message {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 24px;
}

.result-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

/* Support/QR Modal Styles */
.qr-container {
    padding: 20px;
    background: white;
    border-radius: var(--radius);
    display: inline-block;
    margin-bottom: 24px;
}

.qr-image {
    max-width: 250px;
    width: 100%;
    height: auto;
    display: block;
}

.support-message {
    font-size: 1.1rem;
    color: var(--text-primary);
    margin-bottom: 16px;
    line-height: 1.6;
}

/* ===== Keyboard Shortcuts ===== */
.keyboard-shortcuts {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    padding: 10px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 0.85rem;
    color: var(--text-muted);
    display: none;
    backdrop-filter: blur(10px);
}

@media (min-width: 768px) {
    .keyboard-shortcuts {
        display: block;
    }
}

kbd {
    display: inline-block;
    padding: 2px 8px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 4px;
    font-family: monospace;
    font-size: 0.85rem;
    margin: 0 2px;
}

/* ===== Utility Classes ===== */
.text-center {
    text-align: center;
}

.text-left {
    text-align: left;
}

.text-right {
    text-align: right;
}

.text-primary {
    color: var(--text-primary);
}

.text-secondary {
    color: var(--text-secondary);
}

.text-muted {
    color: var(--text-muted);
}

.text-accent {
    color: var(--accent);
}

.text-success {
    color: var(--correct);
}

.text-danger {
    color: var(--incorrect);
}

.font-bold {
    font-weight: 700;
}

/* ===== Mobile Responsiveness ===== */
@media (max-width: 768px) {

    /* Header adjustment for mobile */
    .header-content {
        padding: 12px 16px;
    }

    /* Menu toggle hidden for Bottom Nav */
    .menu-toggle {
        display: none !important;
    }

    /* Main Nav overridden by new M3 Bottom Bar styles at end of file */

    /* Container adjustments */
    .container {
        padding: 16px;
    }

    .chapter-grid {
        grid-template-columns: 1fr;
    }

    .quick-stats,
    .progress-stats {
        flex-direction: column;
        gap: 24px;
    }

    .home-hero h1 {
        font-size: 1.8rem;
    }

    .footer-content {
        flex-direction: column;
        gap: 16px;
    }
}

/* ===== Footer Disclaimer ===== */
.footer-disclaimer {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-style: italic;
    margin-top: 8px;
    opacity: 0.8;
}

/* ===== Toggle Option (New) ===== */
.toggle-option {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    font-size: 0.95rem;
    user-select: none;
    padding: 8px 0;
}

.toggle-option input[type="checkbox"] {
    width: 18px;
    height: 18px;
    accent-color: var(--accent);
    cursor: pointer;
}

/* ===== Subject Selector ===== */
.subject-selector {
    position: relative;
    margin-right: auto;
    margin-left: var(--space-md);
}

.subject-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 14px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-family: var(--font);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.subject-btn:hover {
    border-color: var(--accent);
    background: var(--accent-light);
}

.subject-btn .subject-icon {
    font-size: 1.1rem;
}

.subject-btn .dropdown-arrow {
    font-size: 0.7rem;
    opacity: 0.7;
    transition: transform 0.2s;
}

.subject-dropdown {
    display: none;
    position: absolute;
    top: calc(100% + 8px);
    left: 0;
    min-width: 280px;
    background: var(--bg-card-solid);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    z-index: 200;
    overflow: hidden;
}

.subject-dropdown.active {
    display: block;
    animation: slideDown 0.2s ease;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-8px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.subject-option {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    cursor: pointer;
    transition: var(--transition);
}

.subject-option:hover {
    background: var(--bg-hover);
}

.subject-option.active {
    background: var(--accent-light);
    border-left: 3px solid var(--accent);
}

.subject-option .opt-icon {
    font-size: 1.5rem;
}

.subject-option .opt-info {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.subject-option .opt-name {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.95rem;
}

.subject-option .opt-school {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* Mobile */
@media (max-width: 768px) {
    .subject-selector {
        margin-left: 0;
        order: -1;
        width: 100%;
        margin-bottom: 8px;
    }

    .subject-btn {
        width: 100%;
        justify-content: center;
    }

    .subject-btn .subject-name-short {
        display: none;
    }

    .subject-dropdown {
        width: 100%;
        left: 0;
        right: 0;
    }

    /* Mobile Bottom Navigation - Floating Dock (same as desktop) */
    .main-nav {
        position: fixed;
        bottom: 16px;
        /* Float above bottom edge */
        left: 50%;
        transform: translateX(-50%);
        width: auto;
        max-width: calc(100% - 32px);
        /* Leave margin on sides */
        border-radius: 28px;
        /* Rounded pill shape */
        padding: 8px 12px;
        gap: 4px;
        justify-content: center;
        /* Liquid Glass for mobile */
        background: linear-gradient(135deg,
                rgba(20, 25, 35, 0.8) 0%,
                rgba(35, 40, 55, 0.75) 50%,
                rgba(20, 25, 35, 0.8) 100%);
        backdrop-filter: blur(24px) saturate(1.5);
        -webkit-backdrop-filter: blur(24px) saturate(1.5);
        border: 1px solid rgba(255, 255, 255, 0.12);
        box-shadow:
            0 8px 32px rgba(0, 0, 0, 0.25),
            0 2px 8px rgba(0, 0, 0, 0.15),
            inset 0 1px 1px rgba(255, 255, 255, 0.08);
        margin: 0;
        z-index: 1000;
        height: auto;
        animation: slideUpNav 0.3s ease;
    }

    /* Light mode mobile nav */
    [data-theme="light"] .main-nav {
        background: linear-gradient(135deg,
                rgba(255, 255, 255, 0.75) 0%,
                rgba(248, 250, 255, 0.7) 50%,
                rgba(255, 255, 255, 0.75) 100%);
        border: 1px solid rgba(255, 255, 255, 0.5);
        box-shadow:
            0 8px 32px rgba(0, 0, 0, 0.08),
            0 2px 8px rgba(0, 0, 0, 0.05),
            inset 0 1px 2px rgba(255, 255, 255, 0.8);
    }

    @keyframes slideUpNav {
        from {
            opacity: 0;
            transform: translateX(-50%) translateY(20px);
        }

        to {
            opacity: 1;
            transform: translateX(-50%) translateY(0);
        }
    }

    /* Compact nav tabs for mobile pill */
    .nav-tab {
        flex-direction: column;
        justify-content: center;
        gap: 2px;
        padding: 8px 12px;
        border-radius: 20px;
        background: transparent !important;
        border: none !important;
        box-shadow: none !important;
        color: rgba(255, 255, 255, 0.75);
        flex: 0 0 auto;
        font-size: 10px;
        font-weight: 500;
        white-space: nowrap;
        text-align: center;
        transform: none !important;
    }

    [data-theme="light"] .nav-tab {
        color: rgba(30, 41, 59, 0.75);
    }

    .nav-tab:hover {
        background: rgba(255, 255, 255, 0.1) !important;
        color: rgba(255, 255, 255, 0.95);
    }

    [data-theme="light"] .nav-tab:hover {
        background: rgba(0, 0, 0, 0.05) !important;
        color: rgba(15, 23, 42, 0.95);
    }

    /* Compact icon for mobile */
    .nav-tab .tab-icon {
        display: flex;
        align-items: center;
        justify-content: center;
        width: 40px;
        height: 28px;
        border-radius: 14px;
        transition: all 0.25s cubic-bezier(0.2, 0, 0, 1);
        margin-bottom: 2px;
        font-size: 18px;
        background: transparent;
    }

    .nav-tab.active .tab-icon {
        background: linear-gradient(135deg,
                rgba(124, 58, 237, 0.4) 0%,
                rgba(139, 92, 246, 0.3) 100%);
        color: #ffffff;
        box-shadow:
            0 2px 8px rgba(124, 58, 237, 0.3),
            inset 0 1px 1px rgba(255, 255, 255, 0.15);
    }

    [data-theme="light"] .nav-tab.active .tab-icon {
        background: linear-gradient(135deg,
                rgba(124, 58, 237, 0.3) 0%,
                rgba(139, 92, 246, 0.2) 100%);
        color: #1e40af;
        box-shadow:
            0 2px 8px rgba(124, 58, 237, 0.2),
            inset 0 1px 1px rgba(255, 255, 255, 0.5);
    }

    /* Active tab text */
    .nav-tab.active {
        color: #ffffff;
        background: transparent !important;
    }

    [data-theme="light"] .nav-tab.active {
        color: #1e3a5f;
    }

    .nav-tab span:not(.tab-icon) {
        font-size: 10px;
        line-height: 12px;
        letter-spacing: 0.3px;
    }

    /* Push content up */
    body {
        padding-bottom: 100px;
    }
}

/* Very Small Screens - Hide text labels */
@media (max-width: 380px) {
    .nav-tab span:not(.tab-icon) {
        display: none;
    }

    .nav-tab {
        padding: 8px 10px;
    }

    .main-nav {
        padding: 8px 10px;
        gap: 2px;
    }

    body {
        padding-bottom: 80px;
    }
}

/* ===== Card Spacing Utility ===== */
.md-card+.md-card {
    margin-top: 24px;
}