@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

:root {
  --white: #fff;
  --bg: #f5f6f8;
  --surface: #fff;
  --border: #e2e5ea;
  --border-lt: #eef0f3;
  --text: #1a1a2e;
  --text-mid: #4a4a5a;
  --text-muted: #7c7e8c;
  --text-dim: #a5a7b5;
  --brand: #2b4c8c;
  --accent: #2b7de9;
  --accent-lt: #e8f1fd;
  --green: #1b9e6f;
  --green-bg: #ecfaf3;
  --green-bd: #b8e6d2;
  --red: #d94040;
  --red-bg: #fdf0f0;
  --red-bd: #f0c4c4;
  --yellow: #c28b00;
  --yellow-bg: #fef9ec;
  --yellow-bd: #f0dfa0;
  --hard-color: #d94040;
  --hard-bg: #fdf0f0;
  --hard-bd: #f0c4c4;
  --r: 10px;
  --rs: 7px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: 'Inter', -apple-system, sans-serif; background: var(--bg); color: var(--text); line-height: 1.6; }

/* ── Header ── */
.hdr {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  padding: 0 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  position: sticky;
  top: 0;
  z-index: 50;
  box-shadow: 0 1px 3px rgba(0,0,0,.06);
}
.hdr img { height: 34px; }
.hdr-nav { display: flex; gap: 3px; align-items: center; flex-wrap: wrap; }
.hdr-nav a {
  font-size: 12px; font-weight: 600; color: var(--text-muted);
  text-decoration: none; padding: 6px 11px; border-radius: 5px; transition: .15s;
}
.hdr-nav a:hover { background: var(--bg); color: var(--text); }
.hdr-nav a.on { background: var(--accent-lt); color: var(--accent); }

/* ── Pills / Tags ── */
.pill {
  font-size: 10px; font-weight: 700; text-transform: uppercase;
  letter-spacing: .5px; padding: 3px 10px; border-radius: 20px;
  display: inline-block;
}
.pill-easy { background: var(--green-bg); color: var(--green); border: 1px solid var(--green-bd); }
.pill-medium { background: var(--yellow-bg); color: var(--yellow); border: 1px solid var(--yellow-bd); }
.pill-hard { background: var(--hard-bg); color: var(--hard-color); border: 1px solid var(--hard-bd); }
.pill-topic { background: var(--accent-lt); color: var(--accent); border: 1px solid #c5dafc; }

/* ── Listing Page ── */
.listing-hero {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  padding: 32px 28px 24px;
}
.listing-hero h1 {
  font-size: 28px; font-weight: 800; letter-spacing: -.5px;
  color: var(--text); margin-bottom: 4px;
}
.listing-hero p {
  font-size: 14px; color: var(--text-muted); max-width: 600px;
}
.listing-stats {
  display: flex; gap: 20px; margin-top: 16px;
}
.listing-stat {
  font-size: 13px; color: var(--text-mid); font-weight: 600;
}
.listing-stat strong {
  color: var(--accent); font-size: 20px; display: block; font-weight: 800;
}

.filters {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  padding: 12px 28px;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.filter-label {
  font-size: 11px; font-weight: 700; text-transform: uppercase;
  letter-spacing: .6px; color: var(--text-dim); margin-right: 2px;
}
.filter-btn {
  font-size: 12px; font-weight: 600; padding: 7px 14px;
  border-radius: 20px; border: 1px solid var(--border);
  background: var(--white); color: var(--text-muted);
  cursor: pointer; font-family: 'Inter', sans-serif; transition: .15s;
}
.filter-btn:hover { border-color: var(--accent); color: var(--accent); }
.filter-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.filter-sep {
  width: 1px; height: 24px; background: var(--border); margin: 0 4px;
}
.search-input {
  font-size: 13px; padding: 7px 14px; border-radius: 20px;
  border: 1px solid var(--border); background: var(--white);
  color: var(--text); font-family: 'Inter', sans-serif;
  outline: none; width: 220px; transition: .15s;
}
.search-input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px rgba(43,125,233,.1); }
.search-input::placeholder { color: var(--text-dim); }

.challenge-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
  padding: 24px 28px;
  max-width: 1400px;
}

.challenge-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 20px;
  cursor: pointer;
  transition: .2s;
  text-decoration: none;
  color: inherit;
  display: block;
}
.challenge-card:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 12px rgba(43,125,233,.1);
  transform: translateY(-2px);
}
.card-tags { display: flex; gap: 6px; margin-bottom: 10px; flex-wrap: wrap; }
.card-title {
  font-size: 16px; font-weight: 700; letter-spacing: -.2px;
  margin-bottom: 8px; line-height: 1.3;
}
.card-desc {
  font-size: 13px; color: var(--text-muted); line-height: 1.6;
  display: -webkit-box; -webkit-line-clamp: 2;
  -webkit-box-orient: vertical; overflow: hidden;
}
.no-results {
  grid-column: 1 / -1;
  text-align: center;
  padding: 60px 20px;
  color: var(--text-muted);
  font-size: 15px;
}

/* ── Topic Dropdown ── */
.topic-dropdown {
  position: relative;
}
.topic-dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  margin-top: 6px;
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--rs);
  box-shadow: 0 8px 24px rgba(0,0,0,.1);
  z-index: 40;
  min-width: 260px;
  max-height: 320px;
  overflow-y: auto;
  padding: 6px 0;
}
.topic-dropdown-menu.open { display: block; }
.topic-option {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 14px;
  font-size: 13px;
  color: var(--text-mid);
  cursor: pointer;
  transition: .1s;
}
.topic-option:hover { background: var(--bg); color: var(--text); }
.topic-option.active { color: var(--accent); font-weight: 600; }
.topic-count {
  font-size: 11px;
  color: var(--text-dim);
  font-weight: 600;
  background: var(--bg);
  padding: 1px 8px;
  border-radius: 10px;
}

/* ── Challenge Page Layout ── */
.ch-layout {
  display: grid;
  grid-template-columns: var(--brief-width, 400px) 6px 1fr;
  height: calc(100vh - 64px);
}
@media (max-width: 960px) {
  .ch-layout { grid-template-columns: 1fr !important; }
  .brief-panel { max-height: 50vh; border-right: none !important; border-bottom: 1px solid var(--border); }
  .workspace { height: 55vh; }
  .resizer { display: none; }
}

/* ── Draggable Resizer ── */
.resizer {
  background: var(--border);
  cursor: col-resize;
  width: 6px;
  transition: background .15s;
  position: relative;
}
.resizer:hover, .resizer.active { background: var(--accent); }
.resizer::after {
  content: ''; position: absolute; top: 50%; left: 1px;
  width: 4px; height: 30px; transform: translateY(-50%);
  border-left: 1px solid var(--text-dim); border-right: 1px solid var(--text-dim);
  opacity: .4;
}

/* ── Brief Panel ── */
.brief-panel {
  background: var(--white);
  overflow-y: auto;
  overflow-x: hidden;
  padding: 22px;
  min-width: 280px;
  max-width: 60vw;
}
.ch-back {
  display: inline-flex; align-items: center; gap: 5px;
  font-size: 12px; font-weight: 600; color: var(--text-muted);
  text-decoration: none; margin-bottom: 14px; transition: .15s;
}
.ch-back:hover { color: var(--accent); }
.ch-tags { display: flex; gap: 6px; margin-bottom: 12px; flex-wrap: wrap; }
.ch-title {
  font-size: 21px; font-weight: 800; letter-spacing: -.4px;
  line-height: 1.25; margin-bottom: 18px;
}

.slabel {
  font-size: 10px; font-weight: 700; text-transform: uppercase;
  letter-spacing: .7px; margin-bottom: 8px;
}
.slabel.blue { color: var(--accent); }
.slabel.grey { color: var(--text-muted); }

.scenario {
  background: var(--bg); border: 1px solid var(--border);
  border-radius: var(--r); padding: 16px 18px; margin-bottom: 16px;
}
.scenario p { font-size: 13px; color: var(--text-mid); line-height: 1.7; }
.scenario p + p { margin-top: 7px; }
.scenario strong { color: var(--text); }

.reqs { margin-bottom: 16px; }
.rlist { list-style: none; display: flex; flex-direction: column; gap: 5px; }
.ritem {
  display: flex; align-items: flex-start; gap: 9px;
  padding: 9px 12px; background: var(--bg);
  border: 1px solid var(--border-lt); border-radius: var(--rs);
  font-size: 12px; color: var(--text-mid); line-height: 1.5;
}
.ritem .rtext {
  flex: 1; min-width: 0; overflow-wrap: break-word; word-break: break-word;
}
.ritem .rtext code {
  font-family: 'JetBrains Mono', monospace; font-size: 11px;
  background: var(--accent-lt); padding: 1px 5px; border-radius: 3px;
  color: var(--brand); word-break: break-all;
}
.rbadge {
  flex-shrink: 0; width: 20px; height: 20px; border-radius: 50%;
  background: var(--accent-lt); color: var(--accent);
  font-size: 10px; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}

/* ── Test Table ── */
.tsec { margin-bottom: 16px; }
.ttable {
  width: 100%; border-collapse: separate; border-spacing: 0;
  border: 1px solid var(--border); border-radius: var(--rs);
  overflow: hidden; font-size: 12px;
}
.ttable th {
  background: var(--bg); padding: 7px 10px; text-align: left;
  font-weight: 600; color: var(--text-muted); font-size: 10px;
  text-transform: uppercase; letter-spacing: .4px;
  border-bottom: 1px solid var(--border);
}
.ttable td { padding: 7px 10px; border-bottom: 1px solid var(--border-lt); vertical-align: middle; }
.ttable tr:last-child td { border-bottom: none; }
.ttable .mono { font-family: 'JetBrains Mono', monospace; font-size: 11px; color: var(--text); }
.sc { width: 28px; text-align: center; }
.dot {
  display: inline-flex; align-items: center; justify-content: center;
  width: 20px; height: 20px; border-radius: 50%;
  font-size: 10px; font-weight: 700;
}
.dot-pending { background: var(--bg); border: 1.5px solid var(--border); color: var(--text-dim); }
.dot-pass { background: var(--green-bg); border: 1.5px solid var(--green-bd); color: var(--green); }
.dot-fail { background: var(--red-bg); border: 1.5px solid var(--red-bd); color: var(--red); }

/* ── Hints ── */
.hsec { margin-bottom: 16px; }
.hint-btn {
  display: flex; align-items: center; gap: 7px;
  width: 100%; background: var(--bg); border: 1px solid var(--border-lt);
  border-radius: var(--rs); padding: 9px 12px; cursor: pointer;
  color: var(--text-muted); font-size: 12px; font-weight: 600;
  font-family: 'Inter', sans-serif; transition: .15s;
  margin-bottom: 4px; text-align: left;
}
.hint-btn:hover { border-color: var(--accent); color: var(--accent); }
.hint-arrow { font-size: 8px; transition: transform .2s; }
.hint-btn.open .hint-arrow { transform: rotate(90deg); }
.hint-body {
  display: none; padding: 9px 12px; font-size: 12px;
  color: var(--text-mid); line-height: 1.6;
  background: var(--bg); border: 1px solid var(--border-lt);
  border-radius: var(--rs); margin-bottom: 4px;
}
.hint-body.show { display: block; }
.hint-body code {
  font-family: 'JetBrains Mono', monospace; font-size: 11px;
  background: var(--accent-lt); padding: 1px 5px;
  border-radius: 3px; color: var(--brand);
}

/* ── Extension Box ── */
.ext-box {
  background: #f8f5ff; border: 1px solid #d5cef7;
  border-radius: var(--r); padding: 14px 16px; margin-bottom: 16px;
}
.ext-box .slabel { color: #6c5ce7; }
.ext-box p { font-size: 12px; color: var(--text-mid); line-height: 1.6; }

/* ── AI Feedback Box ── */
.ai-box {
  background: linear-gradient(135deg, #f0f4ff, #f0faf5);
  border: 1px solid #c5dafc; border-radius: var(--r);
  padding: 14px 16px; margin-bottom: 16px; display: none;
}
.ai-box.visible { display: block; animation: fadeSlide .3s ease; }
@keyframes fadeSlide { from { opacity: 0; transform: translateY(5px); } to { opacity: 1; transform: translateY(0); } }
.ai-top { display: flex; align-items: center; gap: 7px; margin-bottom: 8px; }
.ai-tag {
  font-size: 9px; font-weight: 700; text-transform: uppercase;
  letter-spacing: .6px; color: var(--accent); background: var(--accent-lt);
  padding: 2px 7px; border-radius: 3px;
}
.ai-title { font-size: 12px; font-weight: 700; }
.ai-body { font-size: 12px; color: var(--text-mid); line-height: 1.7; }
.ai-body code {
  font-family: 'JetBrains Mono', monospace; font-size: 11px;
  background: #dce6f8; padding: 1px 5px; border-radius: 3px; color: var(--brand);
}

/* ── Description (legacy challenges) ── */
.ch-description {
  background: var(--bg); border: 1px solid var(--border);
  border-radius: var(--r); padding: 16px 18px; margin-bottom: 16px;
}
.ch-description p { font-size: 13px; color: var(--text-mid); line-height: 1.7; }
.ch-hint {
  background: var(--yellow-bg); border: 1px solid var(--yellow-bd);
  border-radius: var(--r); padding: 14px 16px; margin-bottom: 16px;
}
.ch-hint .slabel { color: var(--yellow); }
.ch-hint p { font-size: 12px; color: var(--text-mid); line-height: 1.6; }

/* ── Workspace (Editor) ── */
.workspace {
  display: flex; flex-direction: column;
  background: #fafbfc; height: 100%;
  min-width: 0; overflow: hidden;
}
.editor-bar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 9px 16px; background: var(--white);
  border-bottom: 1px solid var(--border);
}
.file-name {
  font-size: 11px; font-weight: 600;
  font-family: 'JetBrains Mono', monospace;
  color: var(--accent); background: var(--accent-lt);
  padding: 4px 11px; border-radius: 5px;
}
.editor-btns { display: flex; gap: 6px; }
.btn {
  font-family: 'Inter', sans-serif; font-size: 12px; font-weight: 600;
  padding: 6px 14px; border-radius: 6px; border: none;
  cursor: pointer; display: inline-flex; align-items: center;
  gap: 5px; transition: .15s;
}
.btn-ghost {
  background: var(--bg); color: var(--text-muted);
  border: 1px solid var(--border);
}
.btn-ghost:hover { border-color: var(--text-muted); color: var(--text); }
.btn-green { background: var(--green); color: #fff; }
.btn-green:hover { background: #22b47e; }
.btn-blue { background: var(--accent); color: #fff; }
.btn-blue:hover { background: #3b8cf0; }

.editor-wrap {
  flex: 1; overflow: hidden; border-bottom: 1px solid var(--border); position: relative;
}
.editor-wrap .cm-editor {
  height: 100%;
  font-size: 13px;
}
.editor-wrap .cm-editor .cm-scroller {
  font-family: 'JetBrains Mono', monospace;
  line-height: 1.7;
  overflow: auto !important;
}
.editor-wrap .cm-editor.cm-focused { outline: none; }

/* ── Output Panel ── */
.output-panel {
  background: var(--white);
  height: 200px;
  display: flex;
  flex-direction: column;
}
.output-tabs {
  display: flex; align-items: center;
  padding: 5px 16px;
  border-bottom: 1px solid var(--border);
  gap: 3px;
}
.output-tab {
  font-size: 11px; font-weight: 600; padding: 4px 10px;
  border-radius: 4px; background: none; border: none;
  color: var(--text-muted); cursor: pointer;
  font-family: 'Inter', sans-serif;
}
.output-tab.active { background: var(--accent-lt); color: var(--accent); }
.output-body {
  flex: 1; overflow-y: auto; padding: 10px 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px; line-height: 1.6;
  color: var(--text-mid); white-space: pre-wrap;
}
.out-green { color: var(--green); }
.out-red { color: var(--red); }
.out-dim { color: var(--text-dim); }

/* ── Pyodide Loading ── */
.pyodide-loading {
  display: flex; align-items: center; gap: 8px;
  font-size: 12px; color: var(--text-muted);
}
.pyodide-loading .spinner {
  width: 14px; height: 14px; border: 2px solid var(--border);
  border-top-color: var(--accent); border-radius: 50%;
  animation: spin .6s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Scrollbars ── */
.brief-panel::-webkit-scrollbar { width: 4px; }
.brief-panel::-webkit-scrollbar-track { background: transparent; }
.brief-panel::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* ── Footer ── */
.footer {
  background: var(--white);
  border-top: 1px solid var(--border);
  padding: 16px 28px;
  text-align: center;
  font-size: 12px;
  color: var(--text-muted);
}
.footer a { color: var(--accent); text-decoration: none; }
.footer a:hover { text-decoration: underline; }