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

:root {
  --bg: #fff;
  --bg-2: #f8f8f8;
  --text: #111;
  --text-2: #444;
  --text-3: #888;
  --border: #e5e5e5;
  --accent: #2563eb;
  --font: system-ui, -apple-system, sans-serif;
  --mono: 'Menlo', 'Monaco', monospace;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

nav {
  padding: 20px 40px;
  border-bottom: 1px solid var(--border);
}
nav a {
  font-size: 0.8125rem;
  color: var(--text-3);
  text-decoration: none;
}
nav a:hover { color: var(--text); }

main {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 40px 80px;
}

/* Page header */
.page-header {
  padding: 48px 0 36px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 32px;
}

.header-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 28px;
  flex-wrap: wrap;
}

.label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 8px;
}

h1 {
  font-size: 2rem;
  letter-spacing: -0.03em;
  display: flex;
  align-items: baseline;
  gap: 14px;
}

.count {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-3);
  letter-spacing: 0;
}

/* Share button */
.share-btn {
  padding: 9px 18px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-2);
  font-family: var(--font);
  font-size: 0.8125rem;
  border-radius: 6px;
  cursor: pointer;
  transition: border-color 0.15s, color 0.15s;
  white-space: nowrap;
  align-self: center;
}
.share-btn:hover { border-color: #bbb; color: var(--text); }
.share-btn.copied {
  border-color: #22c55e;
  color: #16a34a;
}

/* Filter bar */
.filter-bar {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.pill-group {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.pill {
  padding: 6px 14px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-2);
  font-family: var(--font);
  font-size: 0.8125rem;
  border-radius: 100px;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
}
.pill:hover { border-color: #bbb; color: var(--text); }
.pill.active {
  background: var(--text);
  color: #fff;
  border-color: var(--text);
}

.sort-select {
  padding: 7px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-family: var(--font);
  font-size: 0.8125rem;
  color: var(--text-2);
  background: var(--bg);
  cursor: pointer;
  appearance: none;
  padding-right: 28px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath d='M0 0l5 6 5-6z' fill='%23888'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
}

.search-input {
  padding: 7px 14px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-family: var(--font);
  font-size: 0.8125rem;
  color: var(--text);
  background: var(--bg);
  min-width: 180px;
  flex: 1;
  max-width: 260px;
}
.search-input:focus {
  outline: none;
  border-color: var(--accent);
}

/* Course list */
.course-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0;
}

.course-item {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
  transition: opacity 0.2s;
}
.course-item:last-child { border-bottom: none; }

.course-tag {
  font-size: 0.6875rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 3px 8px;
  border-radius: 4px;
  flex-shrink: 0;
  width: 68px;
  text-align: center;
}
.tag-gsap   { background: #fef9c3; color: #854d0e; }
.tag-css    { background: #ede9fe; color: #5b21b6; }
.tag-d3     { background: #dcfce7; color: #166534; }
.tag-canvas { background: #fee2e2; color: #991b1b; }

.course-body {
  flex: 1;
}
.course-title {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 2px;
}
.course-meta {
  font-size: 0.8125rem;
  color: var(--text-3);
}

/* Empty state */
.empty-state {
  padding: 60px 0;
  text-align: center;
  color: var(--text-3);
  font-size: 0.9375rem;
}
.reset-btn {
  margin-top: 14px;
  padding: 8px 20px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-2);
  font-family: var(--font);
  font-size: 0.875rem;
  border-radius: 6px;
  cursor: pointer;
  transition: border-color 0.15s;
}
.reset-btn:hover { border-color: #bbb; }

@media (max-width: 640px) {
  nav { padding: 16px 20px; }
  main { padding: 0 20px 60px; }
  h1 { font-size: 1.5rem; }
  .filter-bar { gap: 8px; }
  .search-input { max-width: 100%; min-width: 0; width: 100%; }
  .header-top { flex-direction: column; }
  .share-btn { align-self: flex-start; }
}