/* ==========================================================================
   Mathy Club - Global Styles
   ========================================================================== */

/* CSS Custom Properties */
:root {
  --color-cream: #faf6f1;
  --color-cream-dark: #f0ebe4;
  --color-slate: #4a5568;
  --color-slate-light: #718096;
  --color-brown: #8b7355;
  --color-brown-dark: #6b5344;
  --color-rose: #c9a9a6;
  --color-rose-dark: #b08f8c;
  --color-text: #3d3d3d;
  --color-text-muted: #6b6b6b;
  --color-border: #e2ddd7;
  --font-serif: 'Crimson Pro', Georgia, 'Times New Roman', serif;
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
  --max-width: 900px;
  --content-width: 680px;
}

/* Reset */
*, *::before, *::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-serif);
  font-size: 1.125rem;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-cream);
}

/* Typography */
h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-slate);
}

h1 {
  font-size: 2.25rem;
  font-weight: 400;
  letter-spacing: -0.02em;
}

h2 {
  font-size: 1.375rem;
  font-weight: 600;
  margin-top: 0;
  margin-bottom: 1rem;
  color: var(--color-brown-dark);
}

h3 { font-size: 1.125rem; }

p { margin: 0 0 1.25rem; }

a {
  color: var(--color-brown);
  text-decoration: none;
}

a:hover {
  color: var(--color-brown-dark);
  text-decoration: underline;
}

strong {
  font-weight: 600;
  color: var(--color-slate);
}

hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: 2.5rem 0;
}

ul, ol {
  padding-left: 1.25rem;
  margin: 0 0 1.25rem;
}

li { margin-bottom: 0.5rem; }

/* Layout */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Header */
.site-header {
  padding: 1.25rem 0;
  border-bottom: 1px solid var(--color-border);
}

.site-header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-title {
  font-family: var(--font-serif);
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--color-slate);
  text-decoration: none;
  letter-spacing: 0.02em;
}

.site-nav {
  display: flex;
  gap: 1.5rem;
}

.site-nav a {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  color: var(--color-slate-light);
  text-transform: lowercase;
  letter-spacing: 0.03em;
}

.site-nav a:hover,
.site-nav a.active {
  color: var(--color-brown);
  text-decoration: none;
}

/* Main Content */
.site-main {
  padding: 3rem 0;
  min-height: calc(100vh - 180px);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 2rem 0;
  text-align: center;
}

.cc-license {
  color: var(--color-border);
  opacity: 0.5;
  transition: opacity 0.2s;
}

.cc-license:hover {
  opacity: 0.8;
}

/* Homepage */
.home-page {
  max-width: var(--content-width);
  margin: 0 auto;
}

.hero {
  text-align: center;
  padding: 2rem 0 3rem;
}

.hero h1 {
  margin: 0;
  font-size: 2.5rem;
  color: var(--color-slate);
}

.home-content {
  text-align: center;
  color: var(--color-text-muted);
  font-size: 1rem;
}

/* Explorations list */
.explorations {
  margin-top: 3rem;
  text-align: center;
}

.exploration-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.exploration-list li {
  margin: 0.75rem 0;
}

.exploration-list a {
  font-size: 1.25rem;
  color: var(--color-brown);
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 2px;
}

.exploration-list a:hover {
  color: var(--color-brown-dark);
  border-bottom-color: var(--color-brown);
  text-decoration: none;
}

/* Group Overview */
.group-overview {
  max-width: var(--content-width);
  margin: 0 auto;
}

.group-overview .page-header {
  text-align: center;
  margin-bottom: 2rem;
}

.group-overview .page-header h1 {
  margin-bottom: 0.5rem;
}

.group-description {
  text-align: center;
  color: var(--color-text-muted);
}

.duration {
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--color-slate-light);
  text-transform: lowercase;
  letter-spacing: 0.03em;
}

.session-list {
  margin-top: 3rem;
}

.session-list h2 {
  text-align: center;
  font-size: 1rem;
  text-transform: lowercase;
  letter-spacing: 0.05em;
  color: var(--color-slate-light);
  font-weight: 400;
}

.sessions {
  list-style: none;
  padding: 0;
  max-width: 400px;
  margin: 1.5rem auto 0;
}

.sessions li {
  margin: 0;
  border-bottom: 1px solid var(--color-border);
}

.sessions li:first-child {
  border-top: 1px solid var(--color-border);
}

.sessions a {
  display: block;
  padding: 1rem 0;
  color: var(--color-text);
}

.sessions a:hover {
  text-decoration: none;
  color: var(--color-brown);
}

/* Session Layout */
.session-layout {
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: 3rem;
  max-width: var(--max-width);
  margin: 0 auto;
}

.session-sidebar {
  position: sticky;
  top: 2rem;
  align-self: start;
}

.back-link {
  display: block;
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--color-slate-light);
  margin-bottom: 1.5rem;
  text-transform: lowercase;
  letter-spacing: 0.02em;
}

.session-nav h3 {
  font-family: var(--font-sans);
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-slate-light);
  margin: 0 0 0.75rem;
  font-weight: 500;
}

.session-nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.session-nav li {
  margin: 0;
}

.session-nav a {
  display: block;
  padding: 0.4rem 0;
  padding-left: 0.75rem;
  margin-left: -0.75rem;
  border-left: 2px solid transparent;
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.session-nav a:hover {
  color: var(--color-text);
  text-decoration: none;
}

.session-nav .current a {
  color: var(--color-brown);
  border-left-color: var(--color-rose-dark);
}

.session-content {
  max-width: var(--content-width);
}

.session-content .page-header {
  margin-bottom: 2.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--color-border);
}

.session-content .page-header h1 {
  margin: 0;
}

/* Session Pagination */
.session-pagination {
  display: flex;
  justify-content: space-between;
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
  font-family: var(--font-sans);
  font-size: 0.875rem;
}

.session-pagination a {
  color: var(--color-slate-light);
}

.session-pagination a:hover {
  color: var(--color-brown);
  text-decoration: none;
}

/* ==========================================================================
   Slideshow Sections
   ========================================================================== */

.slide-container {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  overflow-y: scroll;
  scroll-snap-type: y mandatory;
  background: var(--color-cream);
  z-index: 100;
}

.slide {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 3rem 0;
  scroll-snap-align: start;
  scroll-snap-stop: always;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

.slide:first-of-type {
  opacity: 1;
  transform: none;
}

.slide.visible {
  opacity: 1;
  transform: none;
}

.slide:last-of-type {
  scroll-snap-align: start;
}

.slide-nav {
  position: fixed;
  top: 1.25rem;
  left: 1.5rem;
  z-index: 101;
  font-family: var(--font-sans);
  font-size: 0.8rem;
}

.slide-nav a {
  color: var(--color-slate-light);
  text-transform: lowercase;
  letter-spacing: 0.02em;
}

.slide-nav a:hover {
  color: var(--color-brown);
  text-decoration: none;
}

/* Intro slide */
.slide-intro h2 {
  font-size: 1.75rem;
  margin-bottom: 0.5rem;
  color: var(--color-slate);
}

.slide-intro p {
  color: var(--color-text-muted);
  margin-bottom: 2.5rem;
}

/* Buttons */
.btn,
a.btn {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 500;
  color: var(--color-cream);
  background: var(--color-brown);
  padding: 1rem 2.5rem;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.2s, transform 0.2s;
}

.btn:hover,
a.btn:hover {
  background: var(--color-brown-dark);
  text-decoration: none;
  transform: translateY(-2px);
}

.btn-outline,
a.btn-outline {
  color: var(--color-brown);
  background: transparent;
  border: 1px solid var(--color-brown);
}

.btn-outline:hover,
a.btn-outline:hover {
  background: var(--color-brown);
  color: var(--color-cream);
}

.slide-nav-links {
  display: flex;
  gap: 1.5rem;
  justify-content: center;
  margin-top: 3rem;
}

.slide-nav-links a {
  display: block;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 500;
  color: var(--color-cream);
  background: var(--color-brown);
  padding: 1rem 2.5rem;
  border-radius: 6px;
  transition: background 0.2s, transform 0.2s;
}

.slide-nav-links a:hover {
  background: var(--color-brown-dark);
  text-decoration: none;
  transform: translateY(-2px);
}

/* Assignment slide */
.slide-assignment {
  background: var(--color-cream-dark);
  scroll-snap-align: start;
}

.slide-assignment .slide-content {
  text-align: left;
  max-width: 540px;
}

.slide-assignment h2 {
  color: var(--color-brown-dark);
  font-size: 1.1rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 1.5rem;
}

.slide-assignment .diagram {
  float: right;
  margin: 0 0 1rem 2rem;
}

.slide-assignment ol,
.slide-assignment ul {
  margin: 0;
  padding-left: 1.25rem;
}

.slide-assignment li {
  margin-bottom: 1rem;
  line-height: 1.6;
}

.slide-assignment li::marker {
  color: var(--color-rose-dark);
  font-weight: 600;
}

/* Notes slide */
.slide-notes {
  background: var(--color-cream);
}

.slide-notes h2 {
  color: var(--color-slate-light);
  font-weight: 400;
}

.slide-content {
  max-width: 500px;
  margin: 0 auto;
  text-align: center;
}

.slide p {
  font-size: 1.25rem;
  color: var(--color-text);
}

.slide .continue {
  display: inline-block;
  margin-top: 2rem;
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--color-rose-dark);
  text-transform: lowercase;
  letter-spacing: 0.05em;
  cursor: pointer;
  border: none;
  background: none;
  padding: 0.5rem 1rem;
}

.slide .continue:hover {
  color: var(--color-brown);
}

/* Diagrams */
.diagram {
  display: flex;
  justify-content: center;
  margin: 2rem 0;
}

.diagram svg {
  color: var(--color-slate);
}

.diagram svg .accent {
  stroke: var(--color-rose-dark);
  fill: var(--color-rose-dark);
}

.diagram svg .accent-fill {
  fill: var(--color-rose-dark);
}

/* Term tooltips */
.term {
  position: relative;
  border-bottom: 1px dotted var(--color-rose-dark);
  cursor: help;
}

.term::after {
  content: attr(data-def);
  position: absolute;
  bottom: 100%;
  left: 50%;
  transform: translateX(-50%) translateY(-4px);
  background: var(--color-slate);
  color: var(--color-cream);
  font-family: var(--font-sans);
  font-size: 0.8rem;
  font-weight: 400;
  line-height: 1.4;
  padding: 0.5rem 0.75rem;
  border-radius: 4px;
  white-space: nowrap;
  max-width: 240px;
  white-space: normal;
  text-align: center;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.2s, visibility 0.2s;
  z-index: 10;
  pointer-events: none;
}

.term::before {
  content: '';
  position: absolute;
  bottom: 100%;
  left: 50%;
  transform: translateX(-50%) translateY(4px);
  border: 6px solid transparent;
  border-top-color: var(--color-slate);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.2s, visibility 0.2s;
  z-index: 10;
}

.term:hover::after,
.term:hover::before,
.term:focus::after,
.term:focus::before {
  opacity: 1;
  visibility: visible;
}

/* Cards */
.card {
  background: var(--color-cream-dark);
  border-radius: 8px;
  padding: 2rem 2.5rem;
  margin: 2.5rem 0;
}

.card h2 {
  font-size: 1rem;
  text-transform: lowercase;
  letter-spacing: 0.03em;
  color: var(--color-slate);
}

.card p:last-child {
  margin-bottom: 0;
}

.card.assignment {
  border-left: 3px solid var(--color-rose-dark);
}

/* Video Embed */
.video-embed {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  margin: 2rem 0;
  border-radius: 8px;
  background: var(--color-cream-dark);
}

.video-embed iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

/* Iframe Embed */
.iframe-embed {
  margin: 2rem 0;
  border-radius: 8px;
  overflow: hidden;
  background: var(--color-cream-dark);
}

.iframe-embed iframe {
  display: block;
  width: 100%;
  height: var(--iframe-height, 400px);
  border: 0;
}

/* ==========================================================================
   Responsive
   ========================================================================== */

@media (max-width: 768px) {
  body {
    font-size: 1.0625rem;
  }

  h1 { font-size: 1.75rem; }

  .session-layout {
    grid-template-columns: 1fr;
    gap: 0;
  }

  .session-sidebar {
    position: static;
    border-bottom: 1px solid var(--color-border);
    padding-bottom: 1.5rem;
    margin-bottom: 2rem;
  }

  .session-nav ul {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
  }

  .session-nav a {
    padding: 0.4rem 0.75rem;
    border: 1px solid var(--color-border);
    border-radius: 4px;
    border-left: 1px solid var(--color-border);
    margin-left: 0;
    font-size: 0.875rem;
  }

  .session-nav .current a {
    border-color: var(--color-rose);
    background: rgba(201, 169, 166, 0.1);
  }

  .slide {
    min-height: 100vh;
    padding: 2rem 1rem;
  }

  .slide-nav {
    left: 1rem;
  }

  .card {
    padding: 1.5rem;
  }
}