/* Subject Cards */
.subjects {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 2rem;
}

.subject-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    overflow: hidden;
    transition: all var(--transition-medium);
    animation: fadeInUp 0.6s ease-out backwards;
}

.subject-card:nth-child(1) { animation-delay: 0.1s; }
.subject-card:nth-child(2) { animation-delay: 0.2s; }
.subject-card:nth-child(3) { animation-delay: 0.3s; }

.subject-card:hover {
    border-color: var(--accent);
    box-shadow: 0 0 0 1px var(--accent-glow), 0 8px 32px rgba(0, 0, 0, 0.12);
}

.subject-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1.25rem 1.5rem;
    cursor: pointer;
    transition: background var(--transition-fast);
}

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

.subject-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border-radius: 12px;
    color: var(--accent);
}

.subject-icon svg {
    width: 24px;
    height: 24px;
}

.subject-info {
    flex: 1;
}

.subject-info h2 {
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.02em;
}

.subject-count {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.expand-btn {
    width: 36px;
    height: 36px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    transition: all var(--transition-fast);
}

.expand-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.expand-btn svg {
    width: 20px;
    height: 20px;
    transition: transform var(--transition-medium);
}

.subject-card.expanded .expand-btn svg {
    transform: rotate(180deg);
}

.subject-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-slow);
}

.subject-card.expanded .subject-content {
    max-height: 2000px;
}

/* Topic Groups */
.topic-group {
    padding: 0 1.5rem 1.5rem;
}

.topic-group:first-child {
    padding-top: 0.5rem;
}

.topic-title {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--text-muted);
    margin-bottom: 0.75rem;
    padding-left: 0.25rem;
}

/* Material Cards */
.materials-grid {
    display: grid;
    gap: 0.5rem;
}

.material-card {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 0.875rem 1rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    border-radius: 10px;
    text-decoration: none;
    color: var(--text-primary);
    transition: all var(--transition-fast);
}

.material-card:hover {
    background: var(--bg-tertiary);
    border-color: var(--border-color);
    transform: translateX(4px);
}

.material-type {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 500;
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    text-transform: uppercase;
}

.material-card[href$=".pdf"] .material-type {
    background: rgba(34, 197, 94, 0.15);
    color: var(--type-pdf);
}

.material-card[href$=".docx"] .material-type,
.material-card[href$=".doc"] .material-type,
.material-card[href$=".rtf"] .material-type {
    background: rgba(59, 130, 246, 0.15);
    color: var(--type-doc);
}

.material-name {
    flex: 1;
    font-size: 0.95rem;
    font-weight: 450;
}

.material-arrow {
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    transition: transform var(--transition-fast), color var(--transition-fast);
}

.material-arrow svg {
    width: 18px;
    height: 18px;
}

.material-card:hover .material-arrow {
    transform: translateX(4px);
    color: var(--accent);
}