/*
Course-aligned light theme inspired by the official Deep Learning page.
*/

:root {
    --bg-color: #ffffff;
    --surface: #ffffff;
    --surface-alt: #f1f3f5;
    --surface-hover: #fff8f4;
    --surface-glass: rgba(255, 255, 255, 0.92);
    --text-primary: #1e1e1e;
    --text-secondary: #5d6470;
    --accent: #ea5b27;
    --accent-hover: #cf4f21;
    --accent-soft: #fff0e9;
    --accent-gradient: linear-gradient(135deg, #ea5b27 0%, #f38b3a 100%);
    --danger: #b42318;
    --success: #067647;
    --warning: #b54708;
    --border: #e6e8ec;
    --ring: rgba(234, 91, 39, 0.25);
    --radius: 14px;
    --radius-sm: 10px;
    --shadow-sm: 0 4px 14px rgba(30, 30, 30, 0.06);
    --shadow: 0 14px 36px rgba(30, 30, 30, 0.12);
    --font-ui: 'Outfit', 'Segoe UI', sans-serif;
}

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

body {
    background: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-ui);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Typography Utility */
.gradient-text {
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    display: inline-block;
}

/* Header */
.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1.25rem;
    background: var(--surface-glass);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 10;
}

.logo-wrap {
    display: flex;
    align-items: center;
    gap: 0.6rem;
}

.site-logo {
    width: 30px;
    height: 30px;
    display: block;
    object-fit: contain;
    border-radius: 7px;
    border: 1px solid rgba(234, 91, 39, 0.15);
    background: #fff;
    box-shadow: 0 3px 10px rgba(234, 91, 39, 0.12);
}

.logo-texts {
    display: flex;
    flex-direction: column;
    line-height: 1.15;
}

.logo-kicker {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-secondary);
    font-weight: 600;
}

.logo-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.timer {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 600;
    font-variant-numeric: tabular-nums;
    background: #fff;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    color: var(--accent);
}

.timer.warning { color: var(--warning); border-color: var(--warning); }
.timer.danger { color: var(--danger); border-color: var(--danger); animation: pulse 1s infinite; }

/* Container */
.container {
    max-width: 1040px;
    margin: 0 auto;
    padding: 2rem;
    flex-grow: 1;
    width: 100%;
}

/* Dashboard */
.hero {
    text-align: center;
    margin-bottom: 2.6rem;
}
.hero h1 {
    font-size: clamp(2rem, 4vw, 2.8rem);
    margin-bottom: 0.8rem;
    letter-spacing: -0.03em;
}
.hero p {
    color: var(--text-secondary);
    max-width: 720px;
    margin: 0 auto;
    font-size: 1.05rem;
}

.dashboard-scoring {
    margin-bottom: 2rem;
    background: #ffffff;
    border-color: #dfe3e8;
    box-shadow: var(--shadow-sm);
}

.dashboard-scoring h3 {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.dashboard-scoring > p {
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.dashboard-main {
    display: grid;
    grid-template-columns: minmax(0, 1.15fr) minmax(300px, 0.85fr);
    gap: 1.5rem;
    align-items: start;
}

.dashboard-actions {
    display: flex;
}

.cards-stack {
    width: 100%;
    grid-template-columns: 1fr;
}

.cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
    position: relative;
    overflow: hidden;
}

.card.interactive {
    cursor: pointer;
}

.card.interactive:hover {
    transform: translateY(-4px) scale(1.01);
    border-color: var(--accent);
    box-shadow: var(--shadow);
}

.card.disabled-card {
    pointer-events: none;
    cursor: not-allowed;
    background: #f3f4f6;
    border-color: #d1d5db;
    color: #6b7280;
    box-shadow: none;
    opacity: 0.9;
}

.card.disabled-card .card-content h3,
.card.disabled-card .card-content p,
.card.disabled-card .badge,
.card.disabled-card .badge.filled {
    color: #6b7280;
}

.card.disabled-card .badge,
.card.disabled-card .badge.filled {
    background: #e5e7eb;
}

.card.disabled-card .card-icon,
.card.disabled-card .card-icon.glow {
    background: #e5e7eb;
    color: #9ca3af;
}

.accent-card {
    border-color: rgba(234, 91, 39, 0.3);
    background: linear-gradient(180deg, #fff8f3 0%, #ffffff 100%);
}
.accent-card:hover {
    box-shadow: var(--shadow);
    border-color: var(--accent);
}

.card-icon {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: rgba(234, 91, 39, 0.1);
    color: var(--accent);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
}
.card-icon.glow {
    background: rgba(234, 91, 39, 0.15);
    color: var(--accent);
}

.card-content h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.card-content p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    flex-grow: 1;
    margin-bottom: 1.5rem;
}

.card-footer {
    display: flex;
    gap: 0.5rem;
}

.badge {
    background: var(--surface-alt);
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.8rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.25rem;
    color: var(--text-primary);
}
.badge.filled {
    background: var(--accent-soft);
    color: var(--accent);
}

/* Exam View */
.exam-header {
    margin-bottom: 2rem;
}

.progress-bar-container {
    height: 6px;
    background: #eceff3;
    border-radius: 999px;
    overflow: hidden;
    margin-bottom: 1rem;
}

.progress-bar-fill {
    height: 100%;
    background: var(--accent-gradient);
    width: 0%;
    transition: width 0.4s ease-out;
}

.exam-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 500;
    color: var(--text-secondary);
}

.btn-info {
    background: transparent;
    border: none;
    color: var(--accent);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-family: inherit;
    font-size: 0.9rem;
    transition: opacity 0.2s;
}
.btn-info:hover { opacity: 0.8; }

.question-container {
    padding: 2rem;
    margin-bottom: 2rem;
    background: #fff;
    box-shadow: var(--shadow-sm);
    min-height: 300px;
}

.q-topic-badge {
    display: inline-block;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--accent);
    font-weight: 700;
    margin-bottom: 1rem;
}

.q-text {
    font-size: 1.25rem;
    font-weight: 500;
    margin-bottom: 2rem;
    line-height: 1.5;
}

.options-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.option-item {
    position: relative;
}

.option-label {
    display: flex;
    align-items: flex-start;
    padding: 1rem 1.25rem;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.2s ease;
    background: #fff;
}

.option-label:hover {
    background: #fff8f3;
    border-color: var(--text-secondary);
}

.option-input {
    position: absolute;
    opacity: 0;
}

/* Custom Checkbox */
.custom-checkbox {
    min-width: 20px;
    height: 20px;
    border: 2px solid var(--text-secondary);
    border-radius: 4px;
    margin-right: 1rem;
    margin-top: 3px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.option-input:checked + .option-label {
    border-color: var(--accent);
    background: var(--accent-soft);
}

.option-input:checked + .option-label .custom-checkbox {
    background: var(--accent);
    border-color: var(--accent);
}

.custom-checkbox::after {
    content: "";
    width: 6px;
    height: 10px;
    border: solid white;
    border-width: 0 2px 2px 0;
    transform: rotate(45deg) scale(0);
    opacity: 0;
    transition: all 0.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.option-input:checked + .option-label .custom-checkbox::after {
    opacity: 1;
    transform: rotate(45deg) scale(1) translateY(-1px);
}

.option-text {
    flex-grow: 1;
}

/* Actions */
.exam-actions {
    display: flex;
    gap: 1rem;
}

.btn {
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-family: inherit;
    font-size: 1rem;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.2s;
    border: 1px solid transparent;
}

.btn.primary {
    background: var(--accent);
    color: #fff;
}
.btn.primary:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
}

.btn.outline {
    background: transparent;
    border-color: var(--border);
    color: var(--text-primary);
}
.btn.outline:hover {
    background: #fff;
    border-color: var(--accent);
    color: var(--accent);
}

.btn.danger {
    background: #fef3f2;
    color: var(--danger);
    border-color: #fecdca;
}
.btn.danger:hover {
    background: #fee4e2;
}

/* Modals */
.modal-backdrop {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(20, 24, 32, 0.12);
    backdrop-filter: none;
    -webkit-backdrop-filter: none;
    z-index: 990;
    opacity: 1;
    transition: opacity 0.3s;
}

.modal {
    position: fixed;
    top: 50%; left: 50%;
    transform: translate(-50%, -50%);
    width: 90%;
    max-width: 600px;
    z-index: 1000;
    isolation: isolate;
}

.modal-content {
    position: relative;
    padding: 2rem;
    background: #ffffff;
    color: var(--text-primary);
    border: 1px solid var(--border);
    box-shadow: 0 20px 48px rgba(20, 24, 32, 0.18);
}

#scoring-info-modal .modal-content {
    background: #ffffff !important;
    color: #1e1e1e !important;
    border-color: #dfe3e8;
    box-shadow: 0 26px 60px rgba(20, 24, 32, 0.22);
}

#scoring-info-modal .info-block {
    background: #fffaf7;
}

.modal-close {
    position: absolute;
    top: 1rem; right: 1rem;
    background: none; border: none;
    color: var(--text-secondary);
    cursor: pointer;
}
.modal-close:hover { color: var(--text-primary); }

.info-grid {
    display: grid;
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.info-block {
    background: #fff;
    padding: 1.25rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
}

.info-icon { font-size: 1.5rem; margin-bottom: 0.5rem; display: block;}
.info-block h4 { margin-bottom: 0.5rem; color: var(--text-primary); }
.info-block p { color: var(--text-secondary); font-size: 0.9rem; }


/* Results View */
.score-banner {
    text-align: center;
    padding: 3rem 2rem;
    margin-bottom: 3rem;
}

.score-display {
    font-size: 4rem;
    font-weight: 700;
    margin: 1rem 0;
}
.actual-score { color: var(--accent); }
.max-score { color: var(--text-secondary); font-size: 2rem; }

.score-stats {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 2rem;
    color: var(--text-secondary);
}

/* Review Section */
.review-subtitle {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.review-item {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
}

.review-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--border);
    padding-bottom: 1rem;
}

.review-score {
    font-weight: 600;
}
.score-perfect { color: var(--success); }
.score-partial { color: var(--warning); }
.score-zero { color: var(--danger); }

.review-qtext {
    font-weight: 500;
    margin-bottom: 1rem;
}

.review-options {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.rev-opt {
    padding: 0.75rem 1rem;
    border-radius: 6px;
    border: 1px solid var(--border);
    background: #fff;
    font-size: 0.95rem;
}

.rev-opt.is-correct {
    border-color: var(--success);
    background: #ecfdf3;
}

.rev-opt.is-selected {
    border-width: 2px;
}

.rev-opt.is-wrong {
    border-color: var(--danger);
    background: #fef3f2;
}

.explanation-box {
    background: #fff8f3;
    border-left: 4px solid var(--accent);
    padding: 1.25rem;
    border-radius: 0 8px 8px 0;
}
.explanation-box h4 {
    color: var(--accent);
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
    text-transform: uppercase;
}

/* Utilities */
.hidden { display: none !important; }
.mt-8 { margin-top: 2rem; }

/* Loaders */
.loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 3rem;
    color: var(--text-secondary);
}

.spinner {
    width: 40px; height: 40px;
    border: 3px solid rgba(234, 91, 39, 0.2);
    border-radius: 50%;
    border-top-color: var(--accent);
    animation: spin 1s ease-in-out infinite;
    margin-bottom: 1rem;
}

/* Animations */
@keyframes spin { to { transform: rotate(360deg); } }
@keyframes pulse { 50% { opacity: .5; } }
@keyframes slideIn { from { opacity: 0; transform: translateY(20px); } to { opacity: 1; transform: translateY(0); } }
@keyframes scaleIn { from { opacity: 0; transform: scale(0.97); } to { opacity: 1; transform: scale(1); } }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

.slide-in { animation: slideIn 0.4s cubic-bezier(0.16, 1, 0.3, 1) forwards; }
.scale-in { animation: scaleIn 0.4s cubic-bezier(0.16, 1, 0.3, 1) forwards; }
.fade-in { animation: fadeIn 0.4s ease forwards; }

/* Responsive */
@media (max-width: 640px) {
    .container { padding: 1rem; }
    .app-header { padding: 0.7rem 0.9rem; }
    .site-logo { width: 24px; height: 24px; }
    .logo-kicker { font-size: 0.65rem; }
    .logo-title { font-size: 0.9rem; }
    .dashboard-main { grid-template-columns: 1fr; }
    .score-display { font-size: 3rem; }
    .exam-actions { flex-direction: column-reverse; }
    .btn { width: 100%; justify-content: center; }
}

math { font-family: 'KaTeX_Math', serif; }