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

:root {
  --bg: #f8f5f0;
  --text: #1a1a1a;
  --accent: #ff6b6b;
  --accent2: #4ecdc4;
  --border: 4px solid black;
  --card-bg: white;
  --timeline-border: #ddd;
  --timeline-dot: var(--accent);
  --footer-border: #ddd;
  --tag-bg: black;
  --tag-text: white;
  --meta-text: #999;
  --subtitle-text: #666;
  --article-text: #555;
}

[data-theme="dark"] {
  --bg: #1a1a1a;
  --text: #f8f5f0;
  --border: 4px solid #f8f5f0;
  --card-bg: #2a2a2a;
  --timeline-border: #444;
  --timeline-dot: var(--accent);
  --footer-border: #444;
  --tag-bg: #f8f5f0;
  --tag-text: #1a1a1a;
  --meta-text: #999;
  --subtitle-text: #aaa;
  --article-text: #bbb;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.7;
  padding: 2rem;
  transition: background 0.3s, color 0.3s;
}

.container {
  max-width: 800px;
  margin: 0 auto;
}

/* Header */
header {
  margin-bottom: 4rem;
}

.header-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 2rem;
  margin-bottom: 1.5rem;
}

h1 {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 900;
  margin-bottom: 1rem;
  line-height: 1.1;
}

.subtitle {
  font-size: 1.3rem;
  color: var(--subtitle-text);
  font-weight: 500;
  margin-bottom: 2rem;
}

/* Theme Toggle */
.theme-toggle {
  background: var(--card-bg);
  border: var(--border);
  padding: 0.8rem;
  cursor: pointer;
  transition: all 0.3s;
  box-shadow: 4px 4px 0 var(--accent);
  position: relative;
  width: 50px;
  height: 50px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

[data-theme="dark"] .theme-toggle {
  box-shadow: 4px 4px 0 #ff6b6b;
}

[data-theme="dark"] .theme-toggle:hover {
  box-shadow: 6px 6px 0 #ff6b6b;
}

.theme-toggle:hover {
  transform: translate(-2px, -2px);
  box-shadow: 6px 6px 0 var(--accent);
}

.theme-toggle svg {
  position: absolute;
  transition: all 0.3s;
}

.theme-toggle .sun-icon {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

.theme-toggle .moon-icon {
  opacity: 0;
  transform: rotate(90deg) scale(0);
}

[data-theme="dark"] .theme-toggle .sun-icon {
  opacity: 0;
  transform: rotate(-90deg) scale(0);
}

[data-theme="dark"] .theme-toggle .moon-icon {
  opacity: 1;
  stroke: white;
  transform: rotate(0deg) scale(1);
}

.contact-links {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  margin-top: 1.5rem;
}

.contact-links a {
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
  padding: 0.5rem 0;
  border-bottom: 3px solid transparent;
  transition: border-color 0.3s;
}

.contact-links a:hover {
  border-bottom-color: var(--accent);
}

/* Sections */
section {
  margin-bottom: 4rem;
}

h2 {
  font-size: 1.8rem;
  font-weight: 900;
  margin-bottom: 2rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  position: relative;
  display: inline-block;
}

h2::after {
  content: "";
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 100%;
  height: 4px;
  background: var(--accent);
}

/* Experiment Cards */
.experiments-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 0.8rem;
}

.experiment-card {
  position: relative;
  height: 100px;
  overflow: hidden;
  text-decoration: none;
  border: 4px solid var(--text);
  transition: all 0.3s ease;
  cursor: pointer;
  background: var(--bg);
  box-shadow: 4px 4px 0 var(--text);
}

.experiment-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-size: cover;
  background-position: center;
  transition: transform 0.3s ease;
  z-index: 0;
  opacity: 0.5;
}

.experiment-card:hover::before {
  transform: scale(1.05);
}

.experiment-card::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.2);
  z-index: 1;
  transition: opacity 0.3s ease;
  opacity: 0;
}

.experiment-card:hover {
  transform: translate(-3px, -3px);
  box-shadow: 7px 7px 0 var(--text);
}

.card-content {
  position: relative;
  z-index: 2;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 1rem;
  text-align: center;
}

.card-content h3 {
  color: var(--text);
  font-size: 1.1rem;
  font-weight: 800;
  line-height: 1.2;
  text-shadow: none;
}

/* Background images - add your image paths here */
.card-wikispeed::before {
  background-image: url("images/wiki.png");
}

.card-group-theory::before {
  background-image: url("path/to/group-theory-image.jpg");
}

.card-neutron::before {
  background-image: url("path/to/neutron-image.jpg");
}

.card-linear::before {
  background-image: url("path/to/linear-image.jpg");
}

.card-ml::before {
  background-image: url("path/to/ml-image.jpg");
}

.card-game-theory::before {
  background-image: url("path/to/game-theory-image.jpg");
}

/* Responsive adjustments for cards */
@media (max-width: 768px) {
  .experiments-grid {
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: 0.7rem;
  }

  .experiment-card {
    height: 90px;
  }

  .card-content h3 {
    font-size: 1rem;
  }
}

@media (max-width: 480px) {
  .experiments-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Timeline Items */
.timeline-item-link {
  text-decoration: none;
  color: inherit;
  display: block;
  margin-bottom: 2.5rem;
}

.timeline-item-link.hidden {
  display: none;
}

.timeline-item {
  padding-left: 1.5rem;
  border-left: 3px solid var(--timeline-border);
  position: relative;
  transition: all 0.3s;
}

.timeline-item-link:hover .timeline-item {
  border-left-color: var(--accent);
}

.timeline-item::before {
  content: "";
  position: absolute;
  left: -7px;
  top: 0;
  width: 11px;
  height: 11px;
  background: var(--timeline-dot);
  border-radius: 50%;
  transition: all 0.3s;
}

.timeline-item-link:hover .timeline-item::before {
  transform: scale(1.3);
}

.timeline-item h3 {
  font-size: 1.4rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.timeline-meta {
  color: var(--meta-text);
  font-weight: 700;
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 0.8rem;
}

.timeline-item p {
  color: var(--article-text);
  font-size: 1.05rem;
  margin-bottom: 0.8rem;
}

/* Tags */
.tags {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-top: 0.8rem;
}

.tag {
  background: var(--tag-bg);
  color: var(--tag-text);
  padding: 0.3rem 0.8rem;
  font-weight: 700;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  transition: background 0.3s, color 0.3s;
}

/* Article Links */
.writing-category {
  margin-bottom: 3rem;
}

.category-title {
  font-size: 1.3rem;
  font-weight: 800;
  margin-bottom: 1.5rem;
  color: var(--text);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.article-link {
  display: block;
  margin-bottom: 2rem;
  padding: 1.5rem;
  background: var(--card-bg);
  border: var(--border);
  text-decoration: none;
  color: var(--text);
  transition: all 0.3s;
  box-shadow: 4px 4px 0 var(--text);
}

.article-link.hidden {
  display: none;
}

.article-link:hover {
  transform: translate(-3px, -3px);
  box-shadow: 7px 7px 0 var(--text);
}

.article-link h4 {
  font-size: 1.3rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.article-link .article-meta {
  color: var(--meta-text);
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  margin-bottom: 0.5rem;
}

.article-link p {
  color: var(--article-text);
  font-size: 1rem;
  line-height: 1.6;
}

/* Expand Button */
.expand-btn {
  background: var(--tag-bg);
  color: var(--tag-text);
  border: var(--border);
  padding: 0.8rem 1.5rem;
  font-weight: 800;
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  cursor: pointer;
  transition: all 0.3s;
  box-shadow: 4px 4px 0 var(--accent);
  margin-top: 1rem;
  display: none;
}

.expand-btn.show {
  display: inline-block;
}

.expand-btn:hover {
  transform: translate(-2px, -2px);
  box-shadow: 6px 6px 0 var(--accent);
}

/* Footer */
footer {
  margin-top: 6rem;
  padding-top: 2rem;
  border-top: 2px solid var(--footer-border);
  text-align: center;
  color: var(--meta-text);
  font-size: 0.9rem;
}

/* Interests Grid */
.interests {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.interest-box {
  background: var(--card-bg);
  border: var(--border);
  padding: 1.5rem;
  text-align: center;
  box-shadow: 3px 3px 0 var(--text);
  transition: background 0.3s, box-shadow 0.3s;
}

.interest-box h4 {
  font-size: 1.1rem;
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.interest-box p {
  font-size: 0.9rem;
  color: var(--article-text);
}

/* Responsive */
@media (max-width: 768px) {
  body {
    padding: 1.5rem;
  }

  h1 {
    font-size: 2rem;
  }

  .subtitle {
    font-size: 1.1rem;
  }

  .header-top {
    flex-direction: column;
    gap: 1rem;
  }

  .theme-toggle {
    align-self: flex-start;
  }

  .contact-links {
    flex-direction: column;
    gap: 0.8rem;
  }

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