/* ============================================================
   Sikorski Design System — 3D Printing Meetup Presentation
   ============================================================ */

/* === Reset === */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

/* === Color System === */
:root {
    --theme-black: #000000;
    --theme-dark-gray: #1c1c1e;
    --theme-light-gray: #f5f5f7;
    --theme-white: #ffffff;

    --bg-color: var(--theme-black);
    --text-color: var(--theme-white);
    --card-bg: rgba(28, 28, 30, 0.7);
    --card-border: rgba(255, 255, 255, 0.1);
    --card-hover: rgba(44, 44, 46, 0.8);
    --btn-bg: var(--theme-white);
    --btn-text: var(--theme-black);
    --btn-hover: #e0e0e0;
    --btn-sec-bg: transparent;
    --btn-sec-border: var(--theme-white);
    --btn-sec-text: var(--theme-white);
    --btn-sec-hover: rgba(255, 255, 255, 0.1);
    --divider: rgba(255, 255, 255, 0.08);
    --text-muted: rgba(255, 255, 255, 0.5);
}

[data-theme="light"] {
    --bg-color: var(--theme-light-gray);
    --text-color: var(--theme-black);
    --card-bg: rgba(255, 255, 255, 0.7);
    --card-border: rgba(0, 0, 0, 0.1);
    --card-hover: rgba(255, 255, 255, 0.9);
    --btn-bg: var(--theme-black);
    --btn-text: var(--theme-white);
    --btn-hover: #333333;
    --btn-sec-bg: transparent;
    --btn-sec-border: var(--theme-black);
    --btn-sec-text: var(--theme-black);
    --btn-sec-hover: rgba(0, 0, 0, 0.05);
    --divider: rgba(0, 0, 0, 0.08);
    --text-muted: rgba(0, 0, 0, 0.5);
}

/* === Base === */
html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    transition: background-color 0.5s ease, color 0.5s ease;
    overflow-x: hidden;
    min-height: 100vh;
}

h1, h2, h3 {
    letter-spacing: -0.04em;
    font-weight: 700;
}

p {
    line-height: 1.6;
    color: inherit;
    opacity: 0.85;
}

a {
    color: inherit;
    text-decoration: none;
}

/* === Navigation === */
.header-nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 30px 50px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 100;
    transition: padding 0.3s ease;
}

.logo {
    color: var(--text-color);
    text-decoration: none;
    font-size: 1rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    transition: color 0.5s ease;
}

.nav-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

.theme-toggle {
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
    width: 28px;
    height: 28px;
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color 0.5s ease;
}

/* === Hero Section === */
.hero-section {
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    padding: 0 20px;
    position: relative;
}

.hero-content {
    max-width: 700px;
    width: 100%;
}

.hero-title {
    font-size: clamp(2.5rem, 5vw, 4rem);
    line-height: 1.1;
    margin-bottom: 16px;
    opacity: 0;
    transform: translateY(30px);
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    max-width: 480px;
    margin: 0 auto 40px;
    opacity: 0;
    transform: translateY(30px);
}

/* Scroll cue — gentle bob + glow pointing down to the presentations */
html {
    scroll-behavior: smooth;
}

.scroll-cue {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin-top: 4px;
    padding: 10px;
    color: var(--text-color);
    opacity: 0;
    cursor: pointer;
    animation: scrollCueIn 0.9s ease 1.6s forwards,
               scrollCueBob 2.2s ease-in-out 2.6s infinite;
    transition: opacity 0.25s ease;
}

.scroll-cue svg {
    animation: scrollCueGlow 2.2s ease-in-out 2.6s infinite;
    transition: transform 0.25s ease;
}

.scroll-cue:hover {
    opacity: 1;
}

.scroll-cue:hover svg {
    transform: scale(1.12);
}

@keyframes scrollCueIn {
    from { opacity: 0; }
    to   { opacity: 0.5; }
}

@keyframes scrollCueBob {
    0%, 100% { transform: translateY(0); }
    50%      { transform: translateY(8px); }
}

@keyframes scrollCueGlow {
    0%, 100% { filter: drop-shadow(0 0 2px currentColor); }
    50%      { filter: drop-shadow(0 0 9px currentColor); }
}

@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }
    .scroll-cue {
        opacity: 0.5;
        animation: none;
    }
    .scroll-cue svg {
        animation: none;
        filter: drop-shadow(0 0 5px currentColor);
    }
}

.hero-cta {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
    opacity: 0;
    transform: translateY(30px);
}

.hero-date {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 20px;
    opacity: 0;
    transform: translateY(30px);
}

/* === Buttons === */
.btn {
    padding: 14px 28px;
    border-radius: 30px;
    font-family: inherit;
    font-weight: 500;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    text-decoration: none;
    display: inline-block;
    -webkit-tap-highlight-color: transparent;
}

.primary-btn {
    background-color: var(--btn-bg);
    color: var(--btn-text);
    border: none;
}

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

.primary-btn:active {
    transform: scale(0.97);
}

.secondary-btn {
    background-color: var(--btn-sec-bg);
    color: var(--btn-sec-text);
    border: 1px solid var(--btn-sec-border);
}

.secondary-btn:hover {
    background-color: var(--btn-sec-hover);
}

.secondary-btn:active {
    transform: scale(0.97);
}

/* === Cards (Glassmorphism) === */
.card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border: 1px solid var(--card-border);
    border-radius: 20px;
    text-decoration: none;
    color: inherit;
    transition: all 0.3s ease;
}

a.card:hover,
button.card:hover {
    background: var(--card-hover);
    transform: translateY(-2px);
}

a.card:active,
button.card:active {
    transform: translateY(0);
}

.card-info {
    flex: 1;
    min-width: 0;
}

.card-title {
    font-size: 1.05rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    margin-bottom: 6px;
}

.card-desc {
    font-size: 0.85rem;
    font-weight: 400;
    opacity: 0.6;
    line-height: 1.5;
}

.card-arrow {
    flex-shrink: 0;
    margin-left: 16px;
    opacity: 0.3;
    transition: opacity 0.3s ease, transform 0.3s ease;
}

a.card:hover .card-arrow,
button.card:hover .card-arrow {
    opacity: 0.7;
    transform: translateX(3px);
}

/* Card grid for topic overview */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 14px;
    margin-bottom: 16px;
}

/* Card stack (vertical list) */
.card-stack {
    display: flex;
    flex-direction: column;
    gap: 14px;
    margin-bottom: 16px;
}

/* === Section Labels & Dividers === */
.section-label {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 20px;
}

.divider {
    width: 100%;
    height: 1px;
    background: var(--divider);
    margin: 48px 0 32px;
}

/* === Content Section === */
.content-section {
    max-width: 1000px;
    width: 100%;
    margin: 0 auto;
    padding: 0 28px 80px;
}

/* === Footer === */
.footer {
    text-align: center;
    font-size: 0.8rem;
    font-weight: 500;
    padding: 60px 28px 48px;
}

.footer-host {
    font-size: 0.95rem;
    font-weight: 600;
    opacity: 0.85;
    margin-bottom: 4px;
}

.footer-host strong {
    font-weight: 700;
}

.footer-tagline {
    font-size: 0.8rem;
    opacity: 0.5;
    margin-bottom: 18px;
}

.footer-links {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
    justify-content: center;
}

.footer-links a {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-color);
    text-decoration: none;
    opacity: 0.6;
    transition: opacity 0.3s ease;
}

.footer-links a:hover {
    opacity: 1;
}

/* === Back Link === */
.back-link {
    display: inline-block;
    font-size: 0.9rem;
    font-weight: 400;
    opacity: 0.5;
    transition: opacity 0.3s ease;
    margin-bottom: 24px;
    text-decoration: none;
    color: inherit;
}

.back-link:hover {
    opacity: 1;
}

/* ============================================================
   PRESENTATION-SPECIFIC STYLES
   ============================================================ */

/* === Slide System === */
.presentation-container {
    width: 100%;
    height: 100vh;
    overflow: hidden;
    position: relative;
}

.slide {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    padding: 120px 40px 110px;
    overflow-y: auto;
    -ms-overflow-style: none;
    scrollbar-width: none;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
}

.slide::-webkit-scrollbar {
    display: none;
}

.slide.active {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.slide-content {
    max-width: 1000px;
    width: 100%;
    position: relative;
    margin: auto 0;
}

/* Slide text elements */
.slide-heading {
    font-size: clamp(2rem, 4vw, 3rem);
    line-height: 1.1;
    margin-bottom: 24px;
}

.slide-body {
    font-size: clamp(1rem, 1.5vw, 1.15rem);
    line-height: 1.7;
    opacity: 0.85;
    max-width: 700px;
    margin-bottom: 32px;
}

.slide-bullets {
    list-style: none;
    padding: 0;
    max-width: 700px;
}

.slide-bullets li {
    font-size: clamp(1rem, 1.5vw, 1.15rem);
    line-height: 1.6;
    opacity: 0.85;
    padding: 12px 0;
    border-bottom: 1px solid var(--divider);
    position: relative;
    padding-left: 24px;
}

.slide-bullets li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--text-color);
    opacity: 0.3;
}

.slide-bullets li:first-child {
    border-top: 1px solid var(--divider);
}

.slide-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-size: 1rem;
    font-weight: 500;
    opacity: 0.7;
    transition: opacity 0.3s ease;
    margin-top: 16px;
}

.slide-link:hover {
    opacity: 1;
}

.slide-link svg {
    transition: transform 0.3s ease;
}

.slide-link:hover svg {
    transform: translateX(3px);
}

.slide-links-row {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-top: 8px;
}

/* === Affiliate / "Buy on Amazon" buttons (data from recommendations.js) === */
.slide-affiliate-group {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 12px;
    margin-top: 18px;
}

.slide-affiliate {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--btn-text);
    background: var(--btn-bg);
    border: 1px solid var(--btn-bg);
    border-radius: 999px;
    transition: opacity 0.3s ease, transform 0.3s ease;
}

.slide-affiliate:hover {
    opacity: 0.85;
    transform: translateY(-1px);
}

.slide-affiliate svg {
    flex-shrink: 0;
}

.slide-affiliate-shop {
    color: var(--text-color);
    background: transparent;
    border: 1px solid var(--btn-sec-border);
}

.affiliate-note {
    width: 100%;
    font-size: 0.72rem;
    font-weight: 400;
    opacity: 0.45;
}

/* Topic badge on slides */
.slide-topic-badge {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 16px;
}

/* === Video Embed === */
.video-container {
    position: relative;
    width: 100%;
    max-width: 800px;
    border-radius: 20px;
    overflow: hidden;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    margin-bottom: 24px;
}

.video-container::before {
    content: '';
    display: block;
    padding-top: 56.25%; /* 16:9 */
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

.video-title {
    font-size: 0.85rem;
    font-weight: 400;
    opacity: 0.5;
    margin-top: 12px;
}

/* === Image & Gallery Embed === */
.slide-image-container {
    width: 100%;
    max-width: 800px;
    margin-bottom: 24px;
    border-radius: 20px;
    overflow: hidden;
    border: 1px solid var(--card-border);
    background: var(--card-bg);
}

.slide-image-container img {
    width: 100%;
    height: auto;
    display: block;
    object-fit: cover;
}

.slide-gallery-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 16px;
    width: 100%;
    max-width: 800px;
    margin-bottom: 24px;
}

.slide-gallery-item {
    border-radius: 16px;
    overflow: hidden;
    border: 1px solid var(--card-border);
    background: var(--card-bg);
}

.slide-gallery-item img {
    width: 100%;
    height: 100%;
    min-height: 200px;
    max-height: 350px;
    display: block;
    object-fit: cover;
}

.slide-image-container img,
.slide-gallery-item img {
    cursor: zoom-in;
}

/* === Image Lightbox (expanded photo view) === */
.image-lightbox {
    position: fixed;
    inset: 0;
    z-index: 2000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 5vmin;
    background: rgba(0, 0, 0, 0.55);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition: opacity 0.3s ease, visibility 0.3s ease;
    cursor: zoom-out;
}

.image-lightbox.visible {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.image-lightbox-img {
    max-width: 92vw;
    max-height: 90vh;
    width: auto;
    height: auto;
    border-radius: 16px;
    border: 1px solid var(--card-border);
    box-shadow: 0 24px 80px rgba(0, 0, 0, 0.5);
    object-fit: contain;
    transform: scale(0.92);
    transition: transform 0.35s cubic-bezier(0.16, 1, 0.3, 1);
    cursor: default;
}

.image-lightbox.visible .image-lightbox-img {
    transform: scale(1);
}

@media (prefers-reduced-motion: reduce) {
    .image-lightbox,
    .image-lightbox-img {
        transition: none;
    }
    .image-lightbox-img {
        transform: none;
    }
}

/* === Progress Bar === */
.progress-bar-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 3px;
    z-index: 150;
    background: transparent;
}

.progress-bar {
    height: 100%;
    width: 0%;
    background: var(--text-color);
    opacity: 0.25;
    transition: width 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

/* === Presenter Controls === */
.presenter-controls {
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    padding: 16px 40px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 100;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border-top: 1px solid var(--card-border);
    transition: transform 0.3s ease;
}

.controls-left,
.controls-center,
.controls-right {
    display: flex;
    align-items: center;
    gap: 12px;
}

.controls-center {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
}

.control-btn {
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: all 0.3s ease;
    opacity: 0.5;
}

.control-btn:hover {
    opacity: 1;
    background: var(--card-hover);
}

.control-btn:active {
    transform: scale(0.93);
}

.control-btn.active {
    opacity: 1;
}

/* Navigation arrows */
.nav-btn {
    width: 44px;
    height: 44px;
    opacity: 0.6;
}

.nav-btn:hover {
    opacity: 1;
}

.nav-btn:disabled {
    opacity: 0.15;
    cursor: default;
    pointer-events: none;
}

/* Slide counter */
.slide-counter {
    font-size: 0.8rem;
    font-weight: 500;
    opacity: 0.5;
    min-width: 60px;
    text-align: center;
    font-variant-numeric: tabular-nums;
}

/* === Slide credit: byline + per-topic contact (Max Sikorski) === */
.slide-credit {
    position: fixed;
    left: 0;
    bottom: 84px;
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 0 20px;
    font-size: 0.72rem;
    font-weight: 500;
    letter-spacing: 0.01em;
    color: var(--text-color);
    opacity: 0.5;
    z-index: 90;
    pointer-events: none; /* don't block the slide or the controls */
    transition: opacity 0.3s ease;
}

.slide-credit:hover {
    opacity: 0.9;
}

.slide-credit-byline strong {
    font-weight: 700;
}

.slide-credit-sep {
    opacity: 0.4;
}

.slide-credit-contact {
    pointer-events: auto; /* but the contact link is clickable */
    display: inline-flex;
    align-items: center;
    gap: 5px;
    color: inherit;
    text-decoration: none;
    opacity: 0.75;
    cursor: pointer;
    transition: opacity 0.2s ease;
}

.slide-credit-contact:hover {
    opacity: 1;
}

.slide-credit-contact svg {
    display: block;
}

/* === Connect (closing) slide === */
.connect-links {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    justify-content: center;
}

.connect-link {
    display: inline-flex;
    align-items: center;
    padding: 12px 22px;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border: 1px solid var(--card-border);
    border-radius: 999px;
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.connect-link:hover {
    background: var(--card-hover);
    transform: translateY(-2px);
}

/* Timer */
.timer-display {
    font-size: 0.85rem;
    font-weight: 500;
    font-variant-numeric: tabular-nums;
    opacity: 0.5;
    cursor: pointer;
    padding: 6px 12px;
    border-radius: 20px;
    transition: all 0.3s ease;
    user-select: none;
    border: none;
    background: none;
    color: var(--text-color);
}

.timer-display:hover {
    opacity: 0.8;
    background: var(--card-hover);
}

.timer-display.warning {
    opacity: 0.8;
}

.timer-display.critical {
    opacity: 1;
    animation: timerPulse 2s ease-in-out infinite;
}

@keyframes timerPulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.4; }
}

/* === TOC Sidebar === */
.toc-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.4);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    z-index: 200;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0.3s ease;
}

.toc-overlay.open {
    opacity: 1;
    visibility: visible;
}

.toc-sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: 340px;
    max-width: 85vw;
    height: 100%;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border-right: 1px solid var(--card-border);
    z-index: 201;
    padding: 80px 32px 32px;
    overflow-y: auto;
    transform: translateX(-100%);
    transition: transform 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

.toc-sidebar.open {
    transform: translateX(0);
}

.toc-title {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 24px;
}

.toc-close {
    position: absolute;
    top: 28px;
    right: 24px;
    background: rgba(128, 128, 128, 0.2);
    border: none;
    color: var(--text-color);
    width: 32px;
    height: 32px;
    border-radius: 50%;
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
}

.toc-close:hover {
    background: rgba(128, 128, 128, 0.4);
}

.toc-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 0;
    border-bottom: 1px solid var(--divider);
    cursor: pointer;
    opacity: 0.5;
    transition: opacity 0.3s ease;
    color: inherit;
    text-decoration: none;
    background: none;
    border-left: none;
    border-right: none;
    border-top: none;
    width: 100%;
    text-align: left;
    font-family: inherit;
}

.toc-item:first-child {
    border-top: 1px solid var(--divider);
}

.toc-item:hover {
    opacity: 0.8;
}

.toc-item.active {
    opacity: 1;
}

.toc-item-number {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-muted);
    min-width: 24px;
}

.toc-item-title {
    font-size: 0.95rem;
    font-weight: 500;
}

/* === QR Code Overlay === */
.qr-overlay {
    position: fixed;
    bottom: 90px;
    right: 40px;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border: 1px solid var(--card-border);
    border-radius: 20px;
    padding: 20px;
    z-index: 150;
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
    transition: all 0.3s ease;
}

.qr-overlay.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.qr-overlay canvas {
    display: block;
    border-radius: 12px;
}

.qr-label {
    font-size: 0.7rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-top: 12px;
    text-align: center;
}

/* === Overview Slide Specific === */
.overview-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 14px;
    width: 100%;
}

.topic-card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border: 1px solid var(--card-border);
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    border-left: none;
    border-right: none;
    border-top: none;
    font-family: inherit;
    color: inherit;
    text-align: left;
    width: 100%;
}

.topic-card:hover {
    background: var(--card-hover);
    transform: translateY(-2px);
}

.topic-card:active {
    transform: translateY(0);
}

.topic-card-info {
    flex: 1;
    min-width: 0;
}

.topic-card-number {
    font-size: 0.7rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 6px;
}

.topic-card-title {
    font-size: 1.05rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    margin-bottom: 6px;
}

.topic-card-desc {
    font-size: 0.85rem;
    font-weight: 400;
    opacity: 0.6;
    line-height: 1.5;
}

.topic-card-arrow {
    flex-shrink: 0;
    margin-left: 16px;
    opacity: 0.3;
    transition: opacity 0.3s ease, transform 0.3s ease;
}

.topic-card:hover .topic-card-arrow {
    opacity: 0.7;
    transform: translateX(3px);
}

/* === Keyboard Hints === */
.keyboard-hints {
    position: fixed;
    bottom: 80px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    gap: 16px;
    opacity: 0;
    transition: opacity 0.5s ease;
    pointer-events: none;
    z-index: 90;
}

.keyboard-hints.visible {
    opacity: 1;
}

.key-hint {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 0.7rem;
    font-weight: 400;
    color: var(--text-muted);
}

.key-hint kbd {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 24px;
    height: 24px;
    padding: 0 6px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 6px;
    font-family: inherit;
    font-size: 0.65rem;
    font-weight: 500;
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
}

/* === Archive Page (index.html) === */
.archive-list {
    display: flex;
    flex-direction: column;
    gap: 14px;
    padding-top: 20px;
}

.archive-card {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px;
    background: var(--card-bg);
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    border: 1px solid var(--card-border);
    border-radius: 20px;
    text-decoration: none;
    color: inherit;
    transition: all 0.3s ease;
}

.archive-card:hover {
    background: var(--card-hover);
    transform: translateY(-2px);
}

.archive-card:active {
    transform: translateY(0);
}

.archive-card-info {
    flex: 1;
    min-width: 0;
}

.archive-card-date {
    font-size: 0.7rem;
    font-weight: 500;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: 6px;
}

.archive-card-title {
    font-size: 1.05rem;
    font-weight: 600;
    letter-spacing: -0.02em;
}

.archive-card-arrow {
    flex-shrink: 0;
    margin-left: 16px;
    opacity: 0.3;
    transition: opacity 0.3s ease, transform 0.3s ease;
}

.archive-card:hover .archive-card-arrow {
    opacity: 0.7;
    transform: translateX(3px);
}

/* === Current ("This Week") featured card === */
.current-section {
    padding-bottom: 28px;
}

.current-list {
    padding-top: 20px;
}

.current-card {
    padding: 32px;
    border-radius: 24px;
}

.current-card .archive-card-date {
    font-size: 0.72rem;
}

.current-card .archive-card-title {
    font-size: 1.5rem;
}

/* === Empty State === */
.empty-state {
    text-align: center;
    padding: 80px 20px;
    opacity: 0.4;
}

.empty-state-icon {
    font-size: 3rem;
    margin-bottom: 16px;
}

.empty-state-text {
    font-size: 1rem;
    font-weight: 400;
}

/* === Loading State === */
.loading-state {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    opacity: 0.4;
}

.loading-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--text-color);
    margin: 0 4px;
    animation: loadingPulse 1.4s ease-in-out infinite;
}

.loading-dot:nth-child(2) {
    animation-delay: 0.2s;
}

.loading-dot:nth-child(3) {
    animation-delay: 0.4s;
}

@keyframes loadingPulse {
    0%, 80%, 100% {
        opacity: 0.2;
        transform: scale(0.8);
    }
    40% {
        opacity: 1;
        transform: scale(1);
    }
}

/* ============================================================
   RESPONSIVE
   ============================================================ */

@media (max-width: 768px) {
    .header-nav {
        padding: 20px;
    }

    .content-section {
        padding: 0 20px 60px;
    }

    .current-card {
        padding: 24px;
    }

    .current-card .archive-card-title {
        font-size: 1.25rem;
    }

    .slide-credit {
        bottom: 74px;
        font-size: 0.66rem;
        gap: 6px;
    }

    .slide {
        padding: 70px 20px 100px;
    }

    .presenter-controls {
        padding: 12px 20px;
    }

    .overview-grid {
        grid-template-columns: 1fr;
    }

    .toc-sidebar {
        width: 100%;
        max-width: 100vw;
    }

    .qr-overlay {
        right: 20px;
        bottom: 80px;
    }

    .keyboard-hints {
        display: none;
    }

    .controls-center {
        position: static;
        transform: none;
    }

    .slide-heading {
        font-size: clamp(1.8rem, 5vw, 2.5rem);
    }

    .video-container {
        border-radius: 12px;
    }
}

@media (max-width: 380px) {
    .hero-title {
        font-size: 2rem;
    }

    .slide-heading {
        font-size: 1.6rem;
    }
}

/* === Header nav text link (e.g. Recommendations) === */
.nav-link {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-color);
    opacity: 0.7;
    transition: opacity 0.3s ease;
    margin-right: 18px;
}

.nav-link:hover {
    opacity: 1;
}

/* === Recommendations / Shop page === */
.rec-intro {
    padding-bottom: 8px;
}

.rec-title {
    font-size: 2.4rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin: 8px 0 10px;
}

.rec-subtitle {
    font-size: 1.05rem;
    opacity: 0.7;
    max-width: 620px;
    margin-bottom: 8px;
}

.rec-disclosure {
    font-size: 0.8rem;
    opacity: 0.45;
    margin-bottom: 28px;
}

.rec-controls {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.rec-search {
    width: 100%;
    max-width: 520px;
    padding: 12px 18px;
    font-family: inherit;
    font-size: 1rem;
    color: var(--text-color);
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 999px;
    outline: none;
    transition: border-color 0.3s ease;
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
}

.rec-search:focus {
    border-color: var(--text-muted);
}

.rec-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.rec-chip {
    padding: 7px 16px;
    font-family: inherit;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-color);
    background: transparent;
    border: 1px solid var(--card-border);
    border-radius: 999px;
    cursor: pointer;
    transition: background 0.25s ease, border-color 0.25s ease, opacity 0.25s ease;
    opacity: 0.7;
}

.rec-chip:hover {
    opacity: 1;
}

.rec-chip.active {
    color: var(--btn-text);
    background: var(--btn-bg);
    border-color: var(--btn-bg);
    opacity: 1;
}

.rec-group {
    margin-top: 36px;
}

.rec-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 16px;
    margin-top: 16px;
}

.rec-card {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    gap: 16px;
    padding: 22px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 18px;
    backdrop-filter: blur(30px);
    -webkit-backdrop-filter: blur(30px);
    transition: border-color 0.3s ease, transform 0.3s ease;
}

.rec-card:hover {
    border-color: var(--text-muted);
    transform: translateY(-2px);
}

.rec-card-name {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: 4px;
}

.rec-card-meta {
    font-size: 0.8rem;
    opacity: 0.5;
    margin-bottom: 10px;
}

.rec-card-note {
    font-size: 0.92rem;
    opacity: 0.75;
    line-height: 1.5;
}

.rec-card-actions {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 12px;
}

.rec-buy {
    display: inline-flex;
    align-items: center;
    padding: 9px 18px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--btn-text);
    background: var(--btn-bg);
    border: 1px solid var(--btn-bg);
    border-radius: 999px;
    transition: opacity 0.3s ease;
}

.rec-buy:hover {
    opacity: 0.85;
}

.rec-brand {
    font-size: 0.85rem;
    font-weight: 500;
    opacity: 0.65;
    transition: opacity 0.3s ease;
}

.rec-brand:hover {
    opacity: 1;
}

.rec-code {
    font-size: 0.8rem;
    font-weight: 600;
    padding: 5px 12px;
    border: 1px dashed var(--card-border);
    border-radius: 8px;
    opacity: 0.8;
}

.rec-soon {
    font-size: 0.82rem;
    opacity: 0.4;
    font-style: italic;
}

.rec-empty {
    margin-top: 40px;
    opacity: 0.5;
}

@media (max-width: 768px) {
    .rec-title {
        font-size: 2rem;
    }
}

/* ============================================================
   Curtain Reveal — opt-in "reveal" slide key (presenter.js)
   Glass curtain over a slide until the button is clicked.
   Added 2026-07-16 (W29 Curve Cut spotlight). Monochrome only.
   ============================================================ */
.slide.reveal-armed {
    overflow: hidden;
}

.slide.reveal-armed .slide-content {
    opacity: 0;
}

.slide-reveal-curtain {
    position: absolute;
    inset: 0;
    z-index: 5;
    overflow: hidden;
}

.slide-reveal-panel {
    position: absolute;
    top: 0;
    bottom: 0;
    width: 50.5%;
    background: var(--card-bg);
    -webkit-backdrop-filter: blur(24px) saturate(140%);
    backdrop-filter: blur(24px) saturate(140%);
    will-change: transform;
}

.slide-reveal-panel-left {
    left: 0;
    border-right: 1px solid var(--card-border);
}

.slide-reveal-panel-right {
    right: 0;
    border-left: 1px solid var(--card-border);
}

.slide-reveal-seam {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 50%;
    width: 1px;
    background: var(--text-color);
    opacity: 0;
    z-index: 6;
    pointer-events: none;
}

.slide-reveal-center {
    position: absolute;
    inset: 0;
    z-index: 7;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 28px;
    text-align: center;
    padding: 40px;
}

.slide-reveal-kicker {
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 0.35em;
    text-transform: uppercase;
    color: var(--text-muted);
}

.slide-reveal-btn {
    font: inherit;
    font-size: 1rem;
    font-weight: 600;
    padding: 16px 44px;
    border-radius: 999px;
    border: 1px solid var(--card-border);
    background: var(--btn-bg);
    color: var(--btn-text);
    cursor: pointer;
    transition: transform 0.3s ease, background 0.3s ease;
}

.slide-reveal-btn:hover {
    background: var(--btn-hover);
    transform: scale(1.04);
}

.slide-reveal-btn:active {
    transform: scale(0.98);
}

.slide-reveal-sweep {
    position: absolute;
    inset: 0;
    z-index: 4;
    pointer-events: none;
    background: linear-gradient(105deg, transparent 40%, var(--reveal-sweep, rgba(255, 255, 255, 0.10)) 50%, transparent 60%);
}

[data-theme="light"] .slide-reveal-sweep {
    --reveal-sweep: rgba(0, 0, 0, 0.06);
}

/* Curtain Reveal extra: confetti (2026-07-16). Piece colors are set inline by
   presenter.js — multicolor by Max's explicit exception to the monochrome rule. */
.slide-reveal-confetti {
    position: absolute;
    inset: 0;
    z-index: 8;
    overflow: hidden;
    pointer-events: none;
}

.slide-reveal-confetti-piece {
    position: absolute;
    top: 0;
    left: 0;
    border-radius: 1px;
    will-change: transform;
}