/* Global Variables & Design Tokens */
:root {
    /* Fonts */
    --font-sans: 'Outfit', sans-serif;
    --font-math: 'Fira Code', monospace;

    /* Dark Mode Palette (Default) */
    --bg-app: radial-gradient(circle at 50% 50%, #0d0f1a 0%, #05060b 100%);
    --bg-card: rgba(18, 22, 41, 0.65);
    --border-card: rgba(255, 255, 255, 0.08);
    --shadow-card: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --text-primary: #f3f4f6;
    --text-secondary: #9ca3af;
    --accent-blue: #3b82f6;
    --accent-blue-glow: rgba(59, 130, 246, 0.3);
    --accent-purple: #8b5cf6;
    --accent-purple-glow: rgba(139, 92, 246, 0.3);
    
    /* State Colors */
    --color-success: #10b981;
    --color-success-bg: rgba(16, 185, 129, 0.15);
    --color-success-border: rgba(16, 185, 129, 0.4);
    
    --color-trap: #f59e0b;
    --color-trap-bg: rgba(245, 158, 11, 0.15);
    --color-trap-border: rgba(245, 158, 11, 0.45);
    
    --color-error: #ef4444;
    --color-error-bg: rgba(239, 68, 68, 0.15);
    --color-error-border: rgba(239, 68, 68, 0.4);

    --border-radius-lg: 18px;
    --border-radius-md: 12px;
    --border-radius-sm: 8px;
    --transition-speed: 0.3s;
}

/* Light Mode Override */
html.light {
    --bg-app: linear-gradient(135deg, #f0f4f8 0%, #e2e8f0 100%);
    --bg-card: rgba(255, 255, 255, 0.85);
    --border-card: rgba(0, 0, 0, 0.06);
    --shadow-card: 0 10px 30px rgba(0, 0, 0, 0.06);
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --accent-blue: #2563eb;
    --accent-blue-glow: rgba(37, 99, 235, 0.15);
    --accent-purple: #7c3aed;
    --accent-purple-glow: rgba(124, 58, 237, 0.15);
    
    --color-success: #059669;
    --color-success-bg: rgba(5, 150, 105, 0.1);
    --color-success-border: rgba(5, 150, 105, 0.25);
    
    --color-trap: #d97706;
    --color-trap-bg: rgba(217, 119, 6, 0.1);
    --color-trap-border: rgba(217, 119, 6, 0.3);
    
    --color-error: #dc2626;
    --color-error-bg: rgba(220, 38, 38, 0.08);
    --color-error-border: rgba(220, 38, 38, 0.2);
}

/* Basic Reset */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-app);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow-x: hidden;
    padding: 20px 10px;
    transition: background var(--transition-speed) ease, color var(--transition-speed) ease;
}

/* Confetti Canvas Overlay */
#confetti-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 10;
}

/* Main Layout Wrapper */
.app-container {
    width: 100%;
    max-width: 680px;
    display: flex;
    flex-direction: column;
    gap: 20px;
    z-index: 2;
}

/* Header */
.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 5px 10px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-icon {
    font-size: 1.8rem;
    animation: rotate 6s linear infinite;
}

.logo h1 {
    font-size: 1.4rem;
    font-weight: 700;
    background: linear-gradient(135deg, #60a5fa, #c084fc);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.5px;
}

.controls {
    display: flex;
    gap: 10px;
}

.control-btn {
    background: var(--bg-card);
    border: 1px solid var(--border-card);
    color: var(--text-primary);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    backdrop-filter: blur(10px);
    transition: all var(--transition-speed) cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow-card);
}

.control-btn:hover {
    transform: translateY(-2px);
    border-color: var(--accent-blue);
    box-shadow: 0 0 12px var(--accent-blue-glow);
}

/* Dashboard Stats Grid */
.dashboard-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}

.stat-card {
    background: var(--bg-card);
    border: 1px solid var(--border-card);
    backdrop-filter: blur(12px);
    border-radius: var(--border-radius-md);
    padding: 12px 8px;
    text-align: center;
    box-shadow: var(--shadow-card);
    transition: transform var(--transition-speed) ease, border-color var(--transition-speed) ease;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow: hidden;
}

.stat-card:hover {
    transform: translateY(-2px);
    border-color: var(--accent-purple);
}

.stat-label {
    font-size: 0.75rem;
    font-weight: 500;
    text-transform: uppercase;
    color: var(--text-secondary);
    letter-spacing: 0.5px;
    margin-bottom: 4px;
}

.stat-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Level Progress Bar */
.progress-bar-container {
    width: 80%;
    height: 4px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 2px;
    margin-top: 6px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    width: 0%;
    background: linear-gradient(90deg, var(--accent-blue), var(--accent-purple));
    transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Main Cards */
.problem-card {
    background: var(--bg-card);
    border: 1px solid var(--border-card);
    backdrop-filter: blur(16px);
    border-radius: var(--border-radius-lg);
    padding: 28px;
    box-shadow: var(--shadow-card);
    position: relative;
    transition: border-color var(--transition-speed) ease;
}

.problem-header {
    text-align: center;
    margin-bottom: 24px;
}

.problem-category {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 20px;
    background: var(--accent-blue-glow);
    color: #93c5fd;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    margin-bottom: 8px;
    border: 1px solid rgba(147, 197, 253, 0.2);
}

html.light .problem-category {
    background: rgba(37, 99, 235, 0.1);
    color: var(--accent-blue);
    border: 1px solid rgba(37, 99, 235, 0.15);
}

.problem-title {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Math Presentation Styles */
.math-display-container {
    background: rgba(0, 0, 0, 0.15);
    border-radius: var(--border-radius-md);
    padding: 24px 10px;
    margin-bottom: 24px;
    display: flex;
    justify-content: center;
    align-items: center;
    border: 1px solid rgba(255, 255, 255, 0.03);
}

html.light .math-display-container {
    background: rgba(255, 255, 255, 0.5);
    border: 1px solid rgba(0, 0, 0, 0.03);
}

.math-equation {
    font-family: var(--font-math);
    font-size: 1.8rem;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-primary);
    user-select: none;
}

/* Fractions structure */
.fraction {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    vertical-align: middle;
    padding: 0 8px;
}

.numerator {
    border-bottom: 2px solid var(--text-primary);
    padding-bottom: 2px;
    text-align: center;
    width: 100%;
}

.denominator {
    padding-top: 2px;
    text-align: center;
    width: 100%;
}

.equals-sign {
    margin: 0 12px;
}

.result-val {
    color: var(--accent-blue);
    font-weight: 600;
}

.math-text {
    font-family: var(--font-sans);
    font-size: 1.4rem;
    text-align: center;
}

/* Answer Inputs & Options */
.answer-section {
    margin-bottom: 24px;
}

.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

#userAnswer {
    width: 100%;
    text-align: center;
    font-family: var(--font-sans);
    font-size: 1.2rem;
    padding: 14px 40px 14px 20px;
    border-radius: var(--border-radius-md);
    border: 2px solid var(--border-card);
    background: rgba(0, 0, 0, 0.2);
    color: var(--text-primary);
    outline: none;
    transition: all var(--transition-speed) ease;
}

html.light #userAnswer {
    background: #fff;
    border-color: #cbd5e1;
}

#userAnswer:focus {
    border-color: var(--accent-blue);
    box-shadow: 0 0 14px var(--accent-blue-glow);
    background: rgba(0, 0, 0, 0.3);
}

html.light #userAnswer:focus {
    background: #fff;
}

.clear-btn {
    position: absolute;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1.5rem;
    cursor: pointer;
    line-height: 1;
    display: none;
}

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

/* Multiple Choices Grid */
.options-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
    margin-top: 10px;
}

.option-btn {
    background: rgba(0, 0, 0, 0.15);
    border: 2px solid var(--border-card);
    color: var(--text-primary);
    padding: 12px;
    border-radius: var(--border-radius-md);
    cursor: pointer;
    font-family: var(--font-sans);
    font-size: 1rem;
    font-weight: 500;
    transition: all 0.2s ease;
    text-align: center;
}

html.light .option-btn {
    background: rgba(255, 255, 255, 0.5);
}

.option-btn:hover {
    border-color: var(--accent-purple);
    transform: translateY(-1px);
    background: rgba(0, 0, 0, 0.25);
}

.option-btn.selected {
    border-color: var(--accent-blue);
    background: var(--accent-blue-glow);
}

/* Action Buttons */
.action-buttons {
    display: flex;
    gap: 14px;
}

.btn {
    flex: 1;
    border: none;
    padding: 14px 20px;
    border-radius: var(--border-radius-md);
    font-family: var(--font-sans);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.btn-primary {
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
    color: #ffffff;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 16px rgba(139, 92, 246, 0.3);
    filter: brightness(1.1);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid var(--border-card);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.15);
    transform: translateY(-2px);
}

html.light .btn-secondary {
    background: #e2e8f0;
    border-color: #cbd5e1;
}
html.light .btn-secondary:hover {
    background: #cbd5e1;
}

.btn:active {
    transform: translateY(0);
}

/* Feedback panel styles */
.feedback-panel {
    margin-top: 24px;
    border-radius: var(--border-radius-md);
    padding: 18px;
    border-width: 1px;
    border-style: solid;
    animation: slideDown 0.3s ease-out;
}

.feedback-header {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 8px;
}

.feedback-title {
    font-size: 1.1rem;
    font-weight: 700;
}

.feedback-panel.success {
    background: var(--color-success-bg);
    border-color: var(--color-success-border);
    color: var(--text-primary);
}

.feedback-panel.success .feedback-icon::before {
    content: "✓";
    color: var(--color-success);
    font-weight: 900;
}

.feedback-panel.trap {
    background: var(--color-trap-bg);
    border-color: var(--color-trap-border);
    color: var(--text-primary);
}

.feedback-panel.trap .feedback-icon::before {
    content: "⚠️";
}

.feedback-panel.error {
    background: var(--color-error-bg);
    border-color: var(--color-error-border);
    color: var(--text-primary);
}

.feedback-panel.error .feedback-icon::before {
    content: "×";
    color: var(--color-error);
    font-size: 1.4rem;
}

/* Step by Step Explainer Subcard */
.explainer-section {
    margin-top: 14px;
    padding-top: 14px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

html.light .explainer-section {
    border-top-color: rgba(0, 0, 0, 0.1);
}

.explainer-title {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.explainer-content {
    font-size: 0.9rem;
    line-height: 1.6;
    color: var(--text-secondary);
}

.explainer-content code, .explainer-content .math-font {
    font-family: var(--font-math);
    background: rgba(0, 0, 0, 0.2);
    padding: 2px 6px;
    border-radius: 4px;
    color: #60a5fa;
}

html.light .explainer-content code, html.light .explainer-content .math-font {
    background: rgba(0, 0, 0, 0.05);
}

/* Info Section (Achievements) */
.info-section {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.info-card {
    background: var(--bg-card);
    border: 1px solid var(--border-card);
    backdrop-filter: blur(12px);
    border-radius: var(--border-radius-md);
    padding: 20px;
    box-shadow: var(--shadow-card);
}

.info-card h3 {
    font-size: 1rem;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.info-card p {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

/* Badges styling */
.badges-container {
    display: flex;
    gap: 12px;
    justify-content: flex-start;
    align-items: center;
    margin-top: 8px;
}

.badge {
    font-size: 1.6rem;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-card);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: help;
    transition: all 0.4s ease;
    user-select: none;
}

.badge.locked {
    filter: grayscale(1) opacity(0.25);
}

.badge.unlocked {
    filter: none;
    background: var(--accent-purple-glow);
    border-color: var(--accent-purple);
    box-shadow: 0 0 10px var(--accent-purple-glow);
    animation: popIn 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

/* App Footer */
.app-footer {
    text-align: center;
    padding: 10px;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* Animations */
@keyframes rotate {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

@keyframes slideDown {
    from { opacity: 0; transform: translateY(-8px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes popIn {
    0% { transform: scale(0.6); opacity: 0; }
    80% { transform: scale(1.1); }
    100% { transform: scale(1); opacity: 1; }
}

.shake {
    animation: shakeAnim 0.4s ease;
}

@keyframes shakeAnim {
    0%, 100% { transform: translateX(0); }
    20%, 60% { transform: translateX(-8px); }
    40%, 80% { transform: translateX(8px); }
}

.hidden {
    display: none !important;
}

/* Responsive Adjustments */
@media (max-width: 600px) {
    .dashboard-stats {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .info-section {
        grid-template-columns: 1fr;
    }
    
    .problem-card {
        padding: 20px;
    }
    
    .math-equation {
        font-size: 1.4rem;
    }
    
    .logo h1 {
        font-size: 1.15rem;
    }
}