:root {
  --bg: #0d0d0d;
  --panel: #141414;
  --border: #00ff41;
  --accent: #ba4df5;
  --text: #e6ffe6;
  --muted: #7f997f;
  --danger: #ff4d4d;
  --warning: #ffcc00;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: 'Courier New', Courier, monospace;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
}

a { color: var(--border); text-decoration: none; }
a:hover { text-decoration: underline; }

header {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
  background: var(--panel);
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

header h1 {
  margin: 0;
  font-size: 1.4rem;
  text-shadow: 0 0 8px var(--border);
}

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

nav button {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--border);
  padding: 0.4rem 0.8rem;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.2s;
}

nav button:hover, nav button.active {
  background: var(--border);
  color: var(--bg);
}

#progress-bar {
  width: 12rem;
  height: 0.6rem;
  background: #222;
  border: 1px solid var(--border);
  border-radius: 3px;
  overflow: hidden;
}

#progress-fill {
  height: 100%;
  width: 0%;
  background: var(--border);
  transition: width 0.3s;
}

main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 1.5rem;
}

.section {
  display: none;
  animation: fade 0.25s ease;
}

.section.active {
  display: block;
}

@keyframes fade {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

.card {
  background: var(--panel);
  border: 1px solid #222;
  border-left: 4px solid var(--border);
  padding: 1rem;
  margin: 1rem 0;
  border-radius: 4px;
}

.card h3 { margin-top: 0; color: var(--border); }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1rem;
}

.tile {
  background: var(--panel);
  border: 1px solid #222;
  padding: 1rem;
  border-radius: 4px;
  cursor: pointer;
  transition: transform 0.15s, border-color 0.15s;
}

.tile:hover {
  transform: translateY(-3px);
  border-color: var(--border);
}

.tile.completed { border-color: var(--border); opacity: 0.75; }

.badge {
  display: inline-block;
  font-size: 0.75rem;
  padding: 0.15rem 0.4rem;
  border-radius: 3px;
  margin-right: 0.4rem;
  text-transform: uppercase;
}

.badge.easy { background: #1b5e20; color: #c8e6c9; }
.badge.medium { background: #f57f17; color: #fff9c4; }
.badge.hard { background: #b71c1c; color: #ffcdd2; }
.badge.points { background: var(--accent); color: #fff; }

input, select, textarea {
  background: #1a1a1a;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.6rem;
  font-family: inherit;
  width: 100%;
  max-width: 400px;
  margin: 0.4rem 0;
}

button.action {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--border);
  padding: 0.6rem 1.2rem;
  cursor: pointer;
  font-family: inherit;
  margin: 0.4rem 0.4rem 0.4rem 0;
}

button.action:hover {
  background: var(--border);
  color: var(--bg);
}

#results {
  margin-top: 1rem;
  padding: 1rem;
  border: 1px solid var(--border);
  background: #0a0a0a;
  min-height: 3rem;
  white-space: pre-wrap;
  position: relative;
}

#results .close-results {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  background: transparent;
  border: 1px solid var(--danger);
  color: var(--danger);
  cursor: pointer;
}

pre {
  background: #0f0f0f;
  padding: 0.8rem;
  overflow-x: auto;
  border: 1px solid #222;
  border-radius: 3px;
}

.tool {
  margin: 1rem 0;
  padding: 1rem;
  border: 1px solid #222;
  border-left: 4px solid var(--accent);
  background: var(--panel);
}

.tool h4 { margin-top: 0; color: var(--accent); }

.toast {
  position: fixed;
  bottom: 1rem;
  right: 1rem;
  padding: 0.8rem 1.2rem;
  border: 1px solid;
  border-radius: 4px;
  background: var(--panel);
  z-index: 200;
}

.toast.success { border-color: var(--border); color: var(--border); }
.toast.error { border-color: var(--danger); color: var(--danger); }

footer {
  text-align: center;
  padding: 2rem;
  color: var(--muted);
  border-top: 1px solid #222;
  margin-top: 2rem;
}

@media (max-width: 600px) {
  header { flex-direction: column; align-items: flex-start; }
  nav { width: 100%; }
  .grid { grid-template-columns: 1fr; }
}