:root, [data-theme="dark"] {
  --bg: #0a0e14;
  --bg-2: #0f141c;
  --bg-3: #151c26;
  --fg: #d6deeb;
  --muted: #6b7a90;
  --border: #1f2937;
  --cyan: #00fff5;
  --red: #ff0055;
  --green: #00ff88;
  --yellow: #ffcc00;
  --purple: #b388ff;
  --mono: 'JetBrains Mono', ui-monospace, 'SFMono-Regular', Menlo, monospace;
  --sans: 'DM Sans', system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
}

[data-theme="light"] {
  --bg: #f5f7fa;
  --bg-2: #ffffff;
  --bg-3: #eef1f5;
  --fg: #1a202c;
  --muted: #64748b;
  --border: #d1d5db;
  --cyan: #0088cc;
  --red: #dc2626;
  --green: #059669;
  --yellow: #d97706;
  --purple: #7c3aed;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--sans);
  font-size: 15px;
  line-height: 1.55;
  min-height: 100vh;
}

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

h1, h2, h3, h4 { font-family: var(--mono); font-weight: 600; letter-spacing: -0.01em; margin: 0.4em 0; }
h1 { color: var(--cyan); font-size: 1.8rem; }
h2 { color: #fff; font-size: 1.3rem; border-bottom: 1px solid var(--border); padding-bottom: .3rem; }
h3 { color: var(--cyan); font-size: 1.05rem; }

code, pre {
  font-family: var(--mono);
  font-size: 0.92em;
  background: #060a10;
  color: #e7eaf3;
  border-radius: 4px;
}
pre { padding: 12px; overflow-x: auto; border: 1px solid var(--border); }
code { padding: 1px 5px; }

/* layout */
header.topbar {
  background: var(--bg-2);
  border-bottom: 1px solid var(--border);
  padding: 12px 24px;
  display: flex;
  align-items: center;
  gap: 18px;
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(8px);
}
header.topbar .logo {
  font-family: var(--mono);
  font-weight: 700;
  color: var(--cyan);
  font-size: 1.15rem;
  letter-spacing: 0.05em;
}
header.topbar nav { display: flex; gap: 16px; flex: 1; }
header.topbar nav a { color: var(--fg); padding: 4px 10px; border-radius: 4px; }
header.topbar nav a:hover, header.topbar nav a.active { background: var(--bg-3); color: var(--cyan); text-decoration: none; }
header.topbar .who { font-family: var(--mono); color: var(--muted); font-size: .85rem; }
header.topbar form { display: inline; }
header.topbar button.logout {
  background: transparent; color: var(--muted); border: 1px solid var(--border);
  padding: 4px 10px; border-radius: 4px; cursor: pointer; font-family: var(--mono); font-size: .8rem;
}
header.topbar button.logout:hover { color: var(--red); border-color: var(--red); }

main { max-width: 1200px; margin: 0 auto; padding: 24px; }
.container-narrow { max-width: 800px; margin: 0 auto; }

/* landing */
.landing {
  min-height: 100vh; display: flex; flex-direction: column;
  align-items: center; justify-content: center; padding: 24px;
  background: radial-gradient(circle at 30% 20%, rgba(0,255,245,.07), transparent 60%),
              radial-gradient(circle at 70% 80%, rgba(255,0,85,.05), transparent 60%);
}
.landing .brand { font-family: var(--mono); color: var(--cyan); font-size: 2.4rem; letter-spacing: 0.08em; }
.landing .tag { color: var(--muted); margin-bottom: 24px; font-family: var(--mono); }
.landing form {
  background: var(--bg-2); border: 1px solid var(--border); border-radius: 8px;
  padding: 24px; min-width: 320px; display: flex; flex-direction: column; gap: 14px;
}
.landing label { font-family: var(--mono); font-size: .8rem; color: var(--muted); text-transform: uppercase; }

input[type=text], input[type=password], input[type=file], select, textarea {
  background: var(--bg); color: var(--fg); border: 1px solid var(--border);
  padding: 10px 12px; border-radius: 5px; font-family: var(--sans); font-size: 14px; width: 100%;
}
textarea { font-family: var(--mono); min-height: 100px; resize: vertical; }
input:focus, select:focus, textarea:focus { outline: none; border-color: var(--cyan); }

button, .btn {
  background: var(--cyan); color: #001216; border: none; padding: 10px 16px;
  border-radius: 5px; font-family: var(--mono); font-weight: 600; cursor: pointer;
  font-size: .9rem; text-transform: uppercase; letter-spacing: .04em;
  display: inline-block; text-align: center;
}
button:hover, .btn:hover { background: #00d4cc; text-decoration: none; }
button.danger, .btn.danger { background: var(--red); color: #fff; }
button.danger:hover, .btn.danger:hover { background: #cc0044; }
button.ghost, .btn.ghost { background: transparent; color: var(--cyan); border: 1px solid var(--cyan); }
button.ghost:hover, .btn.ghost:hover { background: rgba(0,255,245,.1); }
button.warn, .btn.warn { background: var(--yellow); color: #002; }

.error { color: var(--red); font-family: var(--mono); font-size: .9rem; }
.muted { color: var(--muted); font-size: .85rem; font-family: var(--mono); }
.flash { background: rgba(255,204,0,0.1); border: 1px solid var(--yellow); padding: 10px; border-radius: 5px; }

/* filters */
.filters { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 16px; align-items: center; }
.filters .chip {
  padding: 6px 12px; border: 1px solid var(--border); border-radius: 999px;
  font-family: var(--mono); font-size: .8rem; color: var(--muted); cursor: pointer;
}
.filters .chip.active { color: var(--cyan); border-color: var(--cyan); background: rgba(0,255,245,.06); }

/* grid */
.grid { display: grid; gap: 14px; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); }

.card {
  background: var(--bg-2); border: 1px solid var(--border); border-radius: 8px;
  padding: 16px; transition: border-color .15s, transform .15s;
  display: flex; flex-direction: column;
}
.card:hover { border-color: var(--cyan); transform: translateY(-2px); }
.card .code {
  font-family: var(--mono); color: var(--cyan); font-size: .8rem; font-weight: 700; letter-spacing: 0.06em;
}
.card .title { font-weight: 600; margin: 6px 0; color: #fff; }
.card .desc { color: var(--muted); font-size: .9rem; flex: 1; }
.card .meta { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 12px; align-items: center; }
.card .tag {
  font-family: var(--mono); font-size: .7rem; padding: 2px 7px;
  background: var(--bg-3); border-radius: 3px; color: var(--fg);
}

.badge {
  font-family: var(--mono); font-size: .7rem; padding: 3px 8px; border-radius: 3px;
  text-transform: uppercase; letter-spacing: .05em;
}
.badge.easy   { background: rgba(0,255,136,.12);  color: var(--green); }
.badge.medium { background: rgba(255,204,0,.12); color: var(--yellow); }
.badge.hard   { background: rgba(255,0,85,.12);  color: var(--red); }
.badge.boss   { background: rgba(179,136,255,.15); color: var(--purple); }

.status {
  font-family: var(--mono); font-size: .7rem; padding: 3px 8px; border-radius: 3px;
}
.status.not_started     { background: var(--bg-3); color: var(--muted); }
.status.in_progress     { background: rgba(0,255,245,.10); color: var(--cyan); }
.status.submitted       { background: rgba(255,204,0,.12); color: var(--yellow); }
.status.needs_revision  { background: rgba(255,128,0,.15); color: #ff9933; }
.status.approved        { background: rgba(0,255,136,.12); color: var(--green); }
.status.failed          { background: rgba(255,0,85,.12); color: var(--red); }

/* detail / work */
.section { background: var(--bg-2); border: 1px solid var(--border); border-radius: 8px; padding: 18px; margin-bottom: 18px; }
.section ul { padding-left: 1.2em; }
.section li { margin: .25em 0; }

.two-col { display: grid; grid-template-columns: 1.5fr 1fr; gap: 18px; }
@media (max-width: 900px) { .two-col { grid-template-columns: 1fr; } }

/* journal */
.journal { display: flex; flex-direction: column; gap: 10px; max-height: 60vh; overflow-y: auto; padding-right: 6px; }
.journal-entry {
  background: var(--bg-3); border-left: 3px solid var(--cyan);
  padding: 10px 14px; border-radius: 4px;
}
.journal-entry .when { font-family: var(--mono); font-size: .75rem; color: var(--muted); margin-bottom: 6px; }
.journal-entry .body { font-size: .92rem; }
.journal-entry .body p:first-child { margin-top: 0; }
.journal-entry .body p:last-child  { margin-bottom: 0; }

/* evidence */
.evidence-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); gap: 10px; }
.evidence-item {
  background: var(--bg-3); border: 1px solid var(--border); border-radius: 5px;
  padding: 10px; font-size: .85rem; word-break: break-word;
}
.evidence-item img { max-width: 100%; border-radius: 3px; margin-bottom: 6px; }
.evidence-item .type {
  font-family: var(--mono); font-size: .7rem; color: var(--cyan); text-transform: uppercase;
}

/* tables */
table { width: 100%; border-collapse: collapse; }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); font-size: .9rem; }
th { font-family: var(--mono); color: var(--muted); font-weight: 500; text-transform: uppercase; font-size: .72rem; letter-spacing: .05em; }
tbody tr:hover { background: var(--bg-3); }

.kv { display: grid; grid-template-columns: max-content 1fr; gap: 6px 14px; font-size: .9rem; }
.kv .k { color: var(--muted); font-family: var(--mono); font-size: .8rem; }

.flag { color: var(--red); font-family: var(--mono); font-size: .8rem; font-weight: 600; }

/* progress bars */
.progress-bar {
  height: 8px; background: var(--bg-3); border-radius: 99px; overflow: hidden; margin-top: 4px;
}
.progress-bar > div {
  height: 100%; background: linear-gradient(90deg, var(--cyan), var(--green));
}

label.check { display: flex; align-items: center; gap: 8px; font-family: var(--mono); font-size: .9rem; cursor: pointer; }
label.check input { width: auto; }

.row-actions { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; margin-top: 10px; }

.foot-help { color: var(--muted); font-size: .75rem; margin-top: 10px; font-family: var(--mono); }

details.section summary { list-style: none; }
details.section summary::-webkit-details-marker { display: none; }
details.section[open] summary .muted { display: none; }

.theme-toggle {
  background: transparent; border: 1px solid var(--border); color: var(--fg);
  width: 32px; height: 32px; border-radius: 4px; cursor: pointer; font-size: 1rem;
  padding: 0; display: flex; align-items: center; justify-content: center;
}
.theme-toggle:hover { border-color: var(--cyan); }

/* Achievements */
.badge-grid { display: flex; flex-wrap: wrap; gap: 10px; }
.achievement {
  background: var(--bg-3); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px 14px; display: flex; align-items: center; gap: 10px;
  font-size: .85rem; min-width: 200px;
}
.achievement.earned { border-color: var(--cyan); background: rgba(0,255,245,.05); }
.achievement .icon { font-size: 1.4rem; }
.achievement .info .name { font-weight: 600; font-family: var(--mono); font-size: .8rem; }
.achievement .info .desc { color: var(--muted); font-size: .75rem; }
.achievement.locked { opacity: 0.4; }
.achievement.locked .icon { filter: grayscale(1); }

/* XP bar */
.xp-bar { display: flex; align-items: center; gap: 12px; margin: 10px 0; }
.xp-bar .bar { flex: 1; height: 10px; background: var(--bg-3); border-radius: 99px; overflow: hidden; }
.xp-bar .bar > div { height: 100%; background: linear-gradient(90deg, var(--cyan), var(--green)); border-radius: 99px; }
.xp-bar .label { font-family: var(--mono); font-size: .85rem; font-weight: 700; color: var(--cyan); white-space: nowrap; }

/* Locked challenge */
.card.locked { opacity: 0.5; pointer-events: none; position: relative; }
.card.locked::after {
  content: '🔒'; position: absolute; top: 10px; right: 12px; font-size: 1.2rem;
}

.btn.small, button.small { padding: 5px 10px; font-size: .75rem; }

/* ── Responsive ─────────────────────────────────────────────────── */

@media (max-width: 768px) {
  html, body { font-size: 14px; }

  /* topbar: stack vertically */
  header.topbar {
    flex-wrap: wrap;
    padding: 10px 14px;
    gap: 8px;
  }
  header.topbar .logo { font-size: 1rem; }
  header.topbar nav {
    order: 3;
    width: 100%;
    gap: 6px;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    padding-bottom: 4px;
  }
  header.topbar nav::-webkit-scrollbar { display: none; }
  header.topbar nav a {
    white-space: nowrap;
    font-size: .85rem;
    padding: 4px 8px;
  }
  header.topbar .who { font-size: .75rem; }
  header.topbar button.logout { font-size: .7rem; padding: 3px 8px; }

  /* main content */
  main { padding: 14px; }

  h1 { font-size: 1.35rem; }
  h2 { font-size: 1.1rem; }
  h3 { font-size: .95rem; }

  /* card grid: single column */
  .grid { grid-template-columns: 1fr; gap: 10px; }

  .card { padding: 12px; }
  .card .title { font-size: .95rem; }
  .card .desc { font-size: .85rem; }

  /* sections */
  .section { padding: 12px; margin-bottom: 12px; }

  /* two-col layout always stacks */
  .two-col { grid-template-columns: 1fr; gap: 12px; }

  /* tables: horizontal scroll */
  table { display: block; overflow-x: auto; -webkit-overflow-scrolling: touch; }
  th, td { padding: 6px 8px; font-size: .82rem; white-space: nowrap; }

  /* landing */
  .landing .brand { font-size: 1.8rem; }
  .landing .tag { font-size: .8rem; }
  .landing form { min-width: unset; width: 100%; max-width: 400px; padding: 16px; }

  /* filters */
  .filters { gap: 6px; }
  .filters .chip { padding: 4px 10px; font-size: .75rem; }

  /* evidence grid */
  .evidence-list { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 8px; }

  /* journal */
  .journal { max-height: 50vh; }
  .journal-entry { padding: 8px 10px; }

  /* buttons stack */
  .row-actions { gap: 6px; }
  .btn, button { font-size: .8rem; padding: 8px 12px; }
  .btn.small, button.small { padding: 4px 8px; font-size: .7rem; }

  /* mentor student management: stack action buttons */
  td[style*="display: flex"] {
    flex-direction: column;
    gap: 4px !important;
  }

  /* progress bars */
  .kv { grid-template-columns: 1fr; gap: 4px 0; }
  .kv .k { margin-top: 8px; }

  /* mentor dashboard: student filter */
  div[style*="display: flex"][style*="margin-bottom"] {
    flex-direction: column;
    align-items: stretch !important;
  }
}

@media (max-width: 400px) {
  .landing .brand { font-size: 1.4rem; }
  .landing form { padding: 12px; }
  main { padding: 10px; }
  h1 { font-size: 1.15rem; }
}