:root {
  --color-background-primary: hsl(0, 0%, 100%);
  --color-background-secondary: hsl(0, 0%, 98%);
  --color-text-primary: hsl(220, 15%, 15%);
  --color-text-secondary: hsl(220, 10%, 35%);
  --color-border: hsl(220, 10%, 85%);
  --color-primary: hsl(220, 80%, 55%);
  --border-radius-lg: 14px;
  --lang-js-bg: hsl(45, 95%, 92%);
  --lang-ts-bg: hsl(210, 95%, 92%);
  --lang-py-bg: hsl(140, 70%, 92%);
  --lang-go-bg: hsl(190, 80%, 92%);
  --lang-rust-bg: hsl(20, 85%, 92%);
  --diff-beginner: hsl(145, 55%, 40%);
  --diff-intermediate: hsl(38, 90%, 45%);
  --diff-advanced: hsl(0, 70%, 50%);
}

body.theme-dark {
  --color-background-primary: hsl(220, 18%, 10%);
  --color-background-secondary: hsl(220, 18%, 14%);
  --color-text-primary: hsl(0, 0%, 92%);
  --color-text-secondary: hsl(0, 0%, 70%);
  --color-border: hsl(220, 15%, 25%);
  --color-primary: hsl(220, 90%, 65%);
  --lang-js-bg: hsl(45, 40%, 20%);
  --lang-ts-bg: hsl(210, 40%, 20%);
  --lang-py-bg: hsl(140, 35%, 20%);
  --lang-go-bg: hsl(190, 35%, 20%);
  --lang-rust-bg: hsl(20, 35%, 20%);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family:
    system-ui,
    -apple-system,
    Segoe UI,
    Roboto,
    sans-serif;
  background: var(--color-background-primary);
  color: var(--color-text-primary);
  transition:
    background 0.2s,
    color 0.2s;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 24px;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

h1 {
  font-size: 18px;
  font-weight: 600;
}

.count {
  font-size: 13px;
  color: var(--color-text-secondary);
}

.filters {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 18px;
}

.filter-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}

.filter-label {
  font-size: 12px;
  color: var(--color-text-secondary);
  min-width: 70px;
}

.filter-btn {
  padding: 6px 10px;
  border: 0.5px solid var(--color-border);
  background: var(--color-background-secondary);
  color: var(--color-text-secondary);
  border-radius: 999px;
  font-size: 12px;
  cursor: pointer;
  user-select: none;
  transition: all 0.15s;
}

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

.filter-btn.active {
  border-color: var(--color-primary);
  color: var(--color-primary);
  background: var(--color-background-primary);
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
}

.card {
  border: 0.5px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  background: var(--color-background-secondary);
  padding: 14px;
  transition:
    transform 0.15s,
    box-shadow 0.15s;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.theme-dark .card:hover {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

.card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.icon {
  font-size: 18px;
}

.name {
  font-weight: 600;
  font-size: 14px;
  margin: 0;
}

.desc {
  font-size: 12px;
  color: var(--color-text-secondary);
  margin: 8px 0 12px;
  line-height: 1.5;
}

.tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  align-items: center;
}

.pill {
  font-size: 11px;
  padding: 4px 8px;
  border-radius: 999px;
  border: 0.5px solid var(--color-border);
}

.lang-js {
  background: var(--lang-js-bg);
}
.lang-ts {
  background: var(--lang-ts-bg);
}
.lang-py {
  background: var(--lang-py-bg);
}
.lang-go {
  background: var(--lang-go-bg);
}
.lang-rust {
  background: var(--lang-rust-bg);
}

.difficulty {
  font-size: 11px;
  padding: 4px 8px;
  border-radius: 999px;
  color: white;
  font-weight: 500;
}

.beginner {
  background: var(--diff-beginner);
}
.intermediate {
  background: var(--diff-intermediate);
}
.advanced {
  background: var(--diff-advanced);
}

.link {
  display: inline-block;
  margin-top: 10px;
  font-size: 12px;
  color: var(--color-primary);
  text-decoration: none;
  font-weight: 500;
}

.link:hover {
  text-decoration: underline;
}

.theme-toggle {
  border: 0.5px solid var(--color-border);
  background: transparent;
  color: var(--color-text-primary);
  padding: 6px 10px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 12px;
  transition: all 0.15s;
}

.theme-toggle:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--color-text-secondary);
  font-size: 14px;
  grid-column: 1 / -1;
}