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

/* Dark mode (default) */
:root,
[data-theme="dark"] {
  --bg: #000;
  --text: #fff;
  --text-muted: #888;
  --border: #333;
  --border-focus: #666;
  --input-placeholder: #444;
  --btn-bg: #fff;
  --btn-text: #000;
  --error: #ff4444;
  --logo-invert: 1;
  --toggle-icon: "☼";
}

/* Light mode */
[data-theme="light"] {
  --bg: #fff;
  --text: #000;
  --text-muted: #666;
  --border: #ddd;
  --border-focus: #999;
  --input-placeholder: #aaa;
  --btn-bg: #000;
  --btn-text: #fff;
  --error: #cc0000;
  --logo-invert: 0;
  --toggle-icon: "☽";
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background-color: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  transition: background-color 0.2s, color 0.2s;
}

/* Theme toggle button */
.theme-toggle {
  position: fixed;
  top: 1rem;
  right: 1rem;
  background: transparent;
  border: none;
  cursor: pointer;
  font-size: 2rem;
  padding: 0.5rem;
  line-height: 1;
  transition: opacity 0.2s;
}

.theme-toggle::after {
  content: var(--toggle-icon);
  color: var(--text);
}

.theme-toggle:hover {
  opacity: 0.7;
}

.login-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
}

.branding {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
}

.logo {
  width: 120px;
  height: auto;
  filter: invert(var(--logo-invert));
  transition: filter 0.2s;
}

.tagline {
  font-size: 0.875rem;
  color: var(--text-muted);
  letter-spacing: 0.1em;
  text-transform: lowercase;
}

.pin-form {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.pin-input {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
  font-size: 1.5rem;
  padding: 0.75rem 1rem;
  text-align: center;
  letter-spacing: 0.5rem;
  width: 200px;
  border-radius: 4px;
  outline: none;
  transition: border-color 0.2s;
}

.pin-input:focus {
  border-color: var(--border-focus);
}

.pin-input::placeholder {
  color: var(--input-placeholder);
  letter-spacing: normal;
}

.submit-btn {
  background: var(--btn-bg);
  color: var(--btn-text);
  border: none;
  padding: 0.75rem 2rem;
  font-size: 1rem;
  cursor: pointer;
  border-radius: 4px;
  transition: opacity 0.2s;
}

.submit-btn:hover {
  opacity: 0.9;
}

.submit-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.error-message {
  color: var(--error);
  font-size: 0.875rem;
  min-height: 1.25rem;
}

/* Homepage styles */
.home-page {
  display: block;
  align-items: initial;
  justify-content: initial;
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background-color: var(--bg);
  z-index: 100;
}

.header-logo img {
  height: 40px;
  width: auto;
  filter: invert(var(--logo-invert));
  transition: filter 0.2s;
}

.header-nav {
  display: flex;
  gap: 2rem;
}

.header-nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.875rem;
  letter-spacing: 0.05em;
  transition: color 0.2s;
}

.header-nav a:hover,
.header-nav a.active {
  color: var(--text);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.header-actions .theme-toggle {
  position: static;
  font-size: 1.5rem;
  padding: 0.25rem;
}

.logout-btn {
  background: transparent;
  color: var(--text-muted);
  border: 1px solid var(--border);
  padding: 0.5rem 1rem;
  font-size: 0.875rem;
  cursor: pointer;
  border-radius: 4px;
  transition: all 0.2s;
}

.logout-btn:hover {
  color: var(--text);
  border-color: var(--border-focus);
}

main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
}

.hero {
  min-height: 60vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 300;
  letter-spacing: 0.02em;
  text-align: center;
}

.section {
  padding: 4rem 0;
  border-top: 1px solid var(--border);
}

.section h2 {
  font-size: 1.5rem;
  font-weight: 500;
  margin-bottom: 2rem;
  letter-spacing: 0.02em;
}

.section-content {
  color: var(--text-muted);
  line-height: 1.6;
}

/* Page styles */
.page-header {
  padding: 3rem 0;
  border-bottom: 1px solid var(--border);
}

.page-header h1 {
  font-size: 2rem;
  font-weight: 400;
  letter-spacing: 0.02em;
}

.content-section {
  padding: 3rem 0;
  color: var(--text-muted);
  line-height: 1.6;
}

/* Projects grid */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 2rem;
  padding: 3rem 0;
}

a.project-card {
  display: block;
  text-decoration: none;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.5rem;
  transition: border-color 0.2s;
}

a.project-card:hover {
  border-color: var(--border-focus);
}

a.project-card h2 {
  color: var(--text);
}

a.project-card p {
  color: var(--text-muted);
}

.project-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 1rem;
  gap: 1rem;
}

.project-header h2 {
  font-size: 1.25rem;
  font-weight: 500;
}

.project-status {
  font-size: 0.75rem;
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
  background: var(--border);
  color: var(--text-muted);
  white-space: nowrap;
}

.project-description {
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 1rem;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  font-size: 0.75rem;
  padding: 0.25rem 0.5rem;
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text-muted);
}

.loading {
  color: var(--text-muted);
  padding: 2rem;
  text-align: center;
}

/* Breadcrumb */
.breadcrumb {
  padding: 1.5rem 0;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.breadcrumb a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s;
}

.breadcrumb a:hover {
  color: var(--text);
}

.breadcrumb span {
  margin: 0 0.5rem;
}

/* Project detail */
.project-detail {
  padding: 2rem 0 4rem;
  max-width: 800px;
}

.project-detail h1 {
  font-size: 2.5rem;
  font-weight: 400;
  margin-bottom: 0.5rem;
}

.project-meta {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 2rem;
}

.project-meta .tag-link {
  color: var(--text) !important;
  text-decoration: underline;
  text-underline-offset: 2px;
}

.project-meta .tag-link:hover {
  opacity: 0.7;
}

.filter-label {
  font-size: 1rem;
  font-weight: 400;
  color: var(--text-muted);
  margin-left: 0.5rem;
}

.clear-filter {
  color: var(--text-muted);
  text-decoration: none;
  margin-left: 0.25rem;
}

.clear-filter:hover {
  color: var(--text);
}

.project-detail h2 {
  font-size: 1.5rem;
  font-weight: 500;
  margin-top: 2.5rem;
  margin-bottom: 1rem;
}

.project-detail h3 {
  font-size: 1.25rem;
  font-weight: 500;
  margin-top: 2rem;
  margin-bottom: 0.75rem;
}

.project-detail p {
  color: var(--text-muted);
  line-height: 1.7;
  margin-bottom: 1rem;
}

.project-detail strong {
  color: var(--text);
}

.project-detail hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 2rem 0;
}

.project-detail ul {
  color: var(--text-muted);
  line-height: 1.7;
  margin-bottom: 1rem;
  padding-left: 1.5rem;
}

.project-detail li {
  margin-bottom: 0.5rem;
}

.project-detail p a,
.project-detail li a,
.project-detail a {
  color: var(--text) !important;
  text-decoration: underline;
  text-underline-offset: 2px;
}

.project-detail a:hover {
  opacity: 0.7;
}

.latex-block {
  display: block;
  text-align: center;
  margin: 1.5rem 0;
  overflow-x: auto;
}

.latex-inline {
  display: inline;
}