:root {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --card-border: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --accent-color: #3b82f6;
    --accent-hover: #2563eb;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --sidebar-width: 300px;
    --header-height: 64px;
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    height: 100vh;
    overflow: hidden;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-color);
}

::-webkit-scrollbar-thumb {
    background: var(--card-border);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* Layout */
.app-container {
    display: grid;
    grid-template-columns: 1fr var(--sidebar-width);
    grid-template-rows: var(--header-height) 1fr;
    height: 100vh;
    width: 100vw;
}

/* Landing Page Layout */
.landing-wrap {
    height: 100vh;
    overflow-y: auto;
    padding: 40px 20px;
    background: radial-gradient(circle at top center, #1e293b 0%, #0f172a 60%);
}

.landing-container {
    max-width: 1000px;
    margin: 0 auto;
}

.hero-section {
    text-align: center;
    margin-bottom: 60px;
    animation: fadeIn 0.8s ease-out;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 32px;
}

.hero-title {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 16px;
    background: linear-gradient(135deg, #60a5fa 0%, #3b82f6 100%);
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 32px;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin-bottom: 60px;
}

.feature-card {
    background: rgba(30, 41, 59, 0.5);
    border: 1px solid var(--card-border);
    padding: 24px;
    border-radius: 16px;
    backdrop-filter: blur(12px);
    transition: transform 0.3s, border-color 0.3s;
}

.feature-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent-color);
}

.feature-icon {
    font-size: 2rem;
    margin-bottom: 16px;
    display: inline-block;
}

.feature-title {
    font-size: 1.1rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.feature-desc {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* Header */
.app-header {
    grid-column: 1 / -1;
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--card-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 24px;
    z-index: 10;
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--accent-color);
    display: flex;
    align-items: center;
    gap: 8px;
}

.header-controls {
    display: flex;
    align-items: center;
    gap: 16px;
}

/* Main Content */
.main-content {
    grid-column: 1 / 2;
    overflow-y: auto;
    padding: 32px;
    scroll-behavior: smooth;
}

.exam-container {
    max-width: 800px;
    margin: 0 auto;
}

/* Sidebar */
.sidebar {
    grid-column: 2 / 3;
    background-color: var(--card-bg);
    border-left: 1px solid var(--card-border);
    display: flex;
    flex-direction: column;
    height: 100%;
    overflow: hidden;
}

.sidebar-header {
    padding: 20px;
    border-bottom: 1px solid var(--card-border);
}

.timer-display {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    font-variant-numeric: tabular-nums;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.timer-label {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.sidebar-content {
    flex: 1;
    overflow-y: auto;
    padding: 20px;
}

.question-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
}

.q-nav-btn {
    aspect-ratio: 1;
    background: transparent;
    border: 1px solid var(--card-border);
    color: var(--text-secondary);
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.q-nav-btn:hover {
    background-color: rgba(59, 130, 246, 0.1);
    border-color: var(--accent-color);
    color: var(--text-primary);
}

.q-nav-btn.answered {
    background-color: rgba(59, 130, 246, 0.2);
    border-color: var(--accent-color);
    color: var(--accent-color);
}

.q-nav-btn.flagged {
    border-color: var(--warning-color);
    color: var(--warning-color);
}

.q-nav-btn.current {
    background-color: var(--accent-color);
    color: white;
    border-color: var(--accent-color);
}

.sidebar-footer {
    padding: 20px;
    border-top: 1px solid var(--card-border);
    display: flex;
    flex-direction: column;
    gap: 12px;
}

/* Question Card */
.question-card {
    background-color: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    padding: 24px;
    margin-bottom: 24px;
    transition: box-shadow 0.3s;
}

.question-card:focus-within {
    box-shadow: 0 0 0 2px var(--accent-color);
}

.question-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 16px;
}

.question-number {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.question-text {
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 20px;
}

.options-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.option-label {
    display: flex;
    align-items: center;
    padding: 16px;
    background-color: rgba(15, 23, 42, 0.5);
    border: 1px solid var(--card-border);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.option-label:hover {
    background-color: rgba(59, 130, 246, 0.05);
    border-color: var(--accent-color);
}

.option-label.selected {
    background-color: rgba(59, 130, 246, 0.15);
    border-color: var(--accent-color);
}

.option-radio {
    margin-right: 12px;
    accent-color: var(--accent-color);
    width: 18px;
    height: 18px;
}

.btn {
    padding: 12px 24px;
    border-radius: 8px;
    border: none;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    font-size: 0.95rem;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.btn-primary {
    background-color: var(--accent-color);
    color: white;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
    background-color: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: 0 6px 16px rgba(59, 130, 246, 0.4);
}

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

.btn-secondary:hover {
    background-color: rgba(255, 255, 255, 0.05);
    border-color: var(--text-secondary);
}

.btn-danger {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--danger-color);
    border: 1px solid transparent;
}

.btn-danger:hover {
    background-color: rgba(239, 68, 68, 0.2);
}

.btn-icon {
    padding: 8px;
    border-radius: 6px;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
}

.btn-icon:hover {
    color: var(--text-primary);
    background-color: rgba(255, 255, 255, 0.05);
}

/* Utilities */
.hidden {
    display: none !important;
}

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

.card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 16px;
    padding: 24px;
}

.msg {
    margin-top: 12px;
    font-size: 0.9rem;
    min-height: 24px;
}

.msg.error {
    color: var(--danger-color);
}

.msg.ok {
    color: var(--success-color);
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

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

/* Responsive */
@media (max-width: 768px) {
    .app-container {
        grid-template-columns: 1fr;
        grid-template-rows: var(--header-height) 1fr auto;
    }

    .sidebar {
        grid-column: 1 / -1;
        grid-row: 3 / 4;
        height: auto;
        border-left: none;
        border-top: 1px solid var(--card-border);
        flex-direction: row;
        align-items: center;
        padding: 12px;
    }

    .sidebar-header,
    .sidebar-footer {
        border: none;
        padding: 0;
    }

    .timer-display {
        font-size: 1.25rem;
        margin: 0;
    }

    .sidebar-content {
        display: none;
    }

    .sidebar-footer {
        margin-left: auto;
        flex-direction: row;
    }

    .hero-title {
        font-size: 2rem;
    }

    .desktop-only {
        display: none;
    }
}