/* Lectures list */
.lectures-header {
    text-align: center;
    padding: 3.5rem 2rem 2.5rem;
    max-width: 700px;
    margin: 0 auto;
}
.lectures-header-badge { margin-bottom: 1.25rem; }

.lectures-header h1 {
    font-size: 2.25rem;
    font-weight: 800;
    margin-bottom: 0.6rem;
    background: linear-gradient(135deg, var(--color-text-primary) 0%, var(--color-text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.02em;
}
.lectures-header-sub {
    font-size: 1rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
}

.lectures-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.25rem;
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 2rem 3rem;
}

.lecture-card {
    position: relative;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border-light);
    border-radius: var(--radius-lg);
    padding: 1.75rem;
    cursor: pointer;
    transition: all var(--transition-normal);
    display: flex;
    flex-direction: column;
    gap: 1rem;
    overflow: hidden;
    animation: cardFadeInUp 0.45s ease both;
    animation-delay: calc(var(--card-i, 0) * 70ms);
}
.lecture-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--color-accent), transparent);
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    opacity: 0.25;
    transition: opacity var(--transition-normal);
}
.lecture-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: var(--shadow-glow);
}
.lecture-card:hover::before { opacity: 1; }

@keyframes cardFadeInUp {
    from { opacity: 0; transform: translateY(20px); }
    to   { opacity: 1; transform: translateY(0); }
}

.lecture-card-number {
    position: absolute;
    top: -8px;
    right: 16px;
    font-size: 3.5rem;
    font-weight: 800;
    color: rgba(255, 255, 255, 0.03);
    line-height: 1;
    pointer-events: none;
    user-select: none;
}

.lecture-card-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-accent-muted);
    border-radius: var(--radius-md);
    transition: all var(--transition-normal);
}
.lecture-card:hover .lecture-card-icon {
    background: rgba(16, 185, 129, 0.25);
    box-shadow: 0 0 16px var(--color-accent-20);
}
.lecture-card-icon svg { width: 24px; height: 24px; color: var(--color-accent); }

.lecture-card-body h3 { font-size: 1.1rem; font-weight: 600; margin-bottom: 0.5rem; }
.lecture-card-body p {
    font-size: 0.85rem;
    color: var(--color-text-secondary);
    line-height: 1.55;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.lecture-card-footer {
    display: flex;
    gap: 0.5rem;
    margin-top: auto;
    padding-top: 0.5rem;
}

.lecture-badge {
    display: inline-flex;
    align-items: center;
    padding: 0.25rem 0.75rem;
    font-size: 0.7rem;
    font-weight: 600;
    border-radius: 100px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}
.lecture-badge.exercise-count {
    background: var(--color-info-10);
    color: var(--color-info);
}

/* Reading body content */
.feature-list,
.step-list { list-style: none; margin-bottom: 1.5rem; }

.feature-list li {
    position: relative;
    padding: 0.6rem 0 0.6rem 1.75rem;
    font-size: 0.95rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
}
.feature-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 1rem;
    width: 8px;
    height: 8px;
    background: var(--color-accent);
    border-radius: 50%;
}
.feature-list li strong { color: var(--color-text-primary); }

.step-list { counter-reset: step; }
.step-list li {
    position: relative;
    padding: 0.75rem 0 0.75rem 2.5rem;
    font-size: 0.95rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
    counter-increment: step;
}
.step-list li::before {
    content: counter(step);
    position: absolute;
    left: 0;
    top: 0.65rem;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-accent-muted);
    color: var(--color-accent);
    font-size: 0.75rem;
    font-weight: 700;
    border-radius: 50%;
}

.command-block {
    background: rgba(0, 0, 0, 0.5);
    border: 1px solid rgba(16, 185, 129, 0.12);
    border-radius: var(--radius-md);
    overflow: hidden;
    margin-bottom: 0.75rem;
}
.cmd-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.6rem 1rem;
    background: rgba(0, 0, 0, 0.3);
    border-bottom: 1px solid var(--color-border-subtle);
}
.cmd-dots { display: flex; gap: 5px; }
.cmd-dots span {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: rgba(75, 85, 99, 0.4);
}
.cmd-dots span:first-child  { background: rgba(239, 68, 68, 0.6); }
.cmd-dots span:nth-child(2) { background: rgba(245, 158, 11, 0.6); }
.cmd-dots span:last-child   { background: rgba(34, 197, 94, 0.6); }

.cmd-label {
    font-size: 0.65rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-text-muted);
}

.cmd-line {
    display: flex;
    align-items: center;
    padding: 0.875rem 1rem;
    gap: 0.75rem;
    border-bottom: 1px solid rgba(75, 85, 99, 0.1);
}
.cmd-line:last-child { border-bottom: none; }
.cmd-prompt {
    color: var(--color-accent);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    font-weight: 600;
    user-select: none;
    opacity: 0.6;
}
.cmd-line code {
    flex: 1;
    font-family: var(--font-mono);
    font-size: 0.88rem;
    color: var(--color-accent);
    word-break: break-all;
}
.cmd-or {
    text-align: center;
    padding: 0.25rem;
    font-size: 0.75rem;
    color: var(--color-text-muted);
    font-style: italic;
    background: rgba(0, 0, 0, 0.2);
}

/* Callouts */
.callout {
    display: flex;
    gap: 0.875rem;
    padding: 1.25rem;
    border-radius: var(--radius-md);
    margin-bottom: 1.5rem;
    align-items: flex-start;
}
.callout svg { flex-shrink: 0; margin-top: 0.15rem; }
.callout p {
    font-size: 0.9rem;
    line-height: 1.65;
    margin: 0;
    color: var(--color-text-secondary);
}
.callout-info {
    background: rgba(59, 130, 246, 0.06);
    border: 1px solid rgba(59, 130, 246, 0.15);
}
.callout-info svg { color: var(--color-info); }
.callout-warn {
    background: rgba(245, 158, 11, 0.06);
    border: 1px solid rgba(245, 158, 11, 0.15);
}
.callout-warn svg { color: var(--color-warning); }

/* Tables */
.options-table-wrap,
.comparison-matrix-wrap { margin: 0 0 1.5rem; overflow-x: auto; }

.comparison-matrix-wrap {
    margin-top: 1rem;
    background: linear-gradient(180deg, rgba(17, 24, 39, 0.6), rgba(17, 24, 39, 0.3));
    border: 1px solid var(--color-border-light);
    border-radius: var(--radius-lg);
}

.options-table,
.comparison-matrix {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.9rem;
}
.options-table thead th,
.comparison-matrix thead th {
    text-align: left;
    padding: 0.75rem 1rem;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-text-muted);
    background: rgba(0, 0, 0, 0.25);
    border-bottom: 1px solid var(--color-border-light);
}
.options-table tbody td,
.comparison-matrix tbody td {
    padding: 0.75rem 1rem;
    color: var(--color-text-secondary);
    border-bottom: 1px solid var(--color-border-light);
    vertical-align: top;
    line-height: 1.5;
}
.comparison-matrix tbody td { padding: 0.85rem 1rem; vertical-align: middle; }
.options-table tbody tr:last-child td,
.comparison-matrix tbody tr:last-child td { border-bottom: none; }
.options-table tbody tr:hover     { background: rgba(255, 255, 255, 0.02); }
.comparison-matrix tbody tr:hover { background: rgba(16, 185, 129, 0.03); }

.options-table code {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    color: var(--color-accent);
    background: var(--color-accent-10);
    padding: 0.1rem 0.35rem;
    border-radius: var(--radius-sm);
    white-space: nowrap;
}
.matrix-label {
    font-weight: 600;
    color: var(--color-text-primary) !important;
}
.matrix-label code {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--color-accent);
    background: rgba(16, 185, 129, 0.08);
    padding: 0.1rem 0.4rem;
    border-radius: var(--radius-sm);
}
.comparison-matrix tbody td:not(.matrix-label) code {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--color-text-primary);
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid var(--color-border-light);
    padding: 0.1rem 0.4rem;
    border-radius: var(--radius-sm);
    white-space: nowrap;
}

.matrix-pill {
    display: inline-block;
    padding: 0.2rem 0.65rem;
    font-size: 0.7rem;
    font-weight: 600;
    border-radius: 100px;
    border: 1px solid;
}
.matrix-pill-low  { color: var(--color-text-secondary); background: rgba(75, 85, 99, 0.15);  border-color: var(--color-border-soft); }
.matrix-pill-med  { color: var(--color-warning);       background: var(--color-warning-10); border-color: var(--color-warning-30); }
.matrix-pill-high { color: var(--color-accent);        background: var(--color-accent-10);  border-color: var(--color-accent-30); }
.matrix-pill-max  { color: var(--color-danger);        background: var(--color-danger-10);  border-color: var(--color-danger-30); }

/* Feature grid / info grid */
.feature-grid-2col {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin-bottom: 1.5rem;
}
.feature-item {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--color-border-light);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    transition: all var(--transition-normal);
}
.feature-item:hover {
    border-color: var(--color-accent-30);
    background: rgba(16, 185, 129, 0.03);
}
.feature-item h4 { font-size: 0.95rem; font-weight: 600; margin-bottom: 0.5rem; color: var(--color-accent); }
.feature-item p {
    font-size: 0.85rem;
    color: var(--color-text-secondary);
    line-height: 1.55;
    margin: 0;
}
.feature-item-wide { grid-column: 1 / -1; }

.info-grid {
    display: grid;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}
.info-pair {
    display: flex;
    gap: 1rem;
    padding: 0.875rem 1rem;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border-light);
    border-radius: var(--radius-md);
}
.info-key {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    min-width: 100px;
    flex-shrink: 0;
}
.info-val { font-size: 0.9rem; color: var(--color-text-primary); }

.section-overview-card {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
    margin-bottom: 1.75rem;
    padding: 1.25rem 1.5rem;
    background: linear-gradient(135deg, rgba(16, 185, 129, 0.04) 0%, rgba(0, 0, 0, 0.3) 100%);
    border: 1px solid var(--color-accent-10);
    border-radius: var(--radius-md);
}
.overview-item { display: flex; flex-direction: column; gap: 0.35rem; }
.overview-label {
    font-size: 0.65rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-text-muted);
}
.overview-value {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--color-accent);
}

/* Q&A list */
.qa-list {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
    margin: 0 0 1.5rem;
}
.qa-item {
    background: rgba(17, 24, 39, 0.45);
    border: 1px solid rgba(75, 85, 99, 0.18);
    border-radius: var(--radius-md);
    overflow: hidden;
    transition: border-color 0.18s ease, background 0.18s ease;
}
.qa-item[open] {
    border-color: var(--color-accent-30);
    background: rgba(16, 185, 129, 0.04);
}

.qa-question {
    list-style: none;
    cursor: pointer;
    padding: 0.85rem 1.1rem;
    display: flex;
    align-items: center;
    gap: 0.85rem;
    color: var(--color-text-primary);
    font-size: 0.94rem;
    line-height: 1.5;
    user-select: none;
    transition: background 0.15s ease;
}
.qa-question::-webkit-details-marker { display: none; }
.qa-question:hover { background: rgba(255, 255, 255, 0.025); }

.qa-num {
    flex-shrink: 0;
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    color: var(--color-accent);
    background: var(--color-accent-10);
    border: 1px solid var(--color-accent-30);
    border-radius: 100px;
    padding: 0.15rem 0.55rem;
}
.qa-q-text { flex: 1; font-weight: 500; }
.qa-q-text code,
.qa-a-text code {
    font-family: var(--font-mono);
    font-size: 0.86em;
    border-radius: 4px;
    padding: 0.05rem 0.35rem;
}
.qa-q-text code {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(75, 85, 99, 0.25);
}
.qa-a-text code {
    color: var(--color-accent-hover);
    background: rgba(16, 185, 129, 0.08);
    border: 1px solid rgba(16, 185, 129, 0.25);
}

.qa-toggle {
    flex-shrink: 0;
    color: var(--color-text-muted);
    transition: transform 0.2s ease, color 0.15s ease;
    opacity: 0.6;
}
.qa-item[open] .qa-toggle {
    transform: rotate(90deg);
    color: var(--color-accent);
    opacity: 1;
}

.qa-answer {
    padding: 0.85rem 1.1rem 1rem;
    border-top: 1px solid rgba(16, 185, 129, 0.18);
    display: flex;
    align-items: baseline;
    gap: 0.85rem;
    background: rgba(0, 0, 0, 0.18);
}
.qa-a-label {
    flex-shrink: 0;
    font-size: 0.62rem;
    font-weight: 700;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--color-accent);
    padding: 0.15rem 0.5rem;
    border: 1px solid var(--color-accent-30);
    border-radius: 4px;
    background: var(--color-accent-10);
}
.qa-a-text { color: var(--color-text-primary); font-size: 0.92rem; line-height: 1.55; }

/* Responsive */
@media (max-width: 900px) {
    .lectures-grid       { grid-template-columns: 1fr; padding: 0 1rem 2rem; }
    .feature-grid-2col   { grid-template-columns: 1fr; }
    .feature-item-wide   { grid-column: auto; }
    .section-overview-card { grid-template-columns: repeat(2, 1fr); }
    .lectures-header     { padding: 2rem 1rem 1.5rem; }
    .lectures-header h1  { font-size: 1.5rem; }
}
@media (max-width: 600px) {
    .cmd-line       { padding: 0.75rem; }
    .cmd-line code  { font-size: 0.8rem; }
    .section-overview-card { grid-template-columns: 1fr 1fr; gap: 0.75rem; padding: 1rem; }
}
@media (hover: none) and (pointer: coarse) {
    .lecture-card:hover  { transform: none; }
    .lecture-card:active { transform: scale(0.98); border-color: var(--color-accent); }
}