:root {
  --bg: #0f172a;
  --surface: #1e293b;
  --text: #f8fafc;
  --muted: #94a3b8;
  --accent: #38bdf8;
  --accent2: #818cf8;
  --success: #34d399;
  --danger: #fb7185;
  --warning: #fbbf24;
  --radius: 14px;
}

* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.45;
  min-height: 100vh;
}
#app { max-width: 960px; margin: 0 auto; padding: 24px; }

h1, h2, h3 { margin: 0 0 12px; }
p { margin: 0 0 12px; color: var(--muted); }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  border: none; border-radius: 10px; padding: 10px 16px; cursor: pointer;
  font-size: 15px; color: #fff; background: linear-gradient(135deg, var(--accent), var(--accent2));
  box-shadow: 0 6px 18px rgba(0,0,0,.25);
  transition: transform .08s ease, box-shadow .2s ease;
}
.btn:hover { transform: translateY(-1px); box-shadow: 0 10px 24px rgba(0,0,0,.3); }
.btn.ghost { background: transparent; box-shadow: none; border: 1px solid rgba(255,255,255,.12); color: var(--text); }
.btn.success { background: linear-gradient(135deg, var(--success), #22c55e); }
.btn.danger { background: linear-gradient(135deg, var(--danger), #f43f5e); }
.btn.sm { padding: 6px 10px; font-size: 13px; }

header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 0; margin-bottom: 16px;
}
header .brand { font-weight: 800; letter-spacing: .3px; }
header .user { display: flex; align-items: center; gap: 10px; font-size: 14px; color: var(--muted); }

.card {
  background: var(--surface);
  border: 1px solid rgba(255,255,255,.06);
  border-radius: var(--radius);
  padding: 18px;
  margin-bottom: 14px;
}

.grid { display: grid; gap: 12px; }
.grid.cols-2 { grid-template-columns: repeat(2, 1fr); }
.grid.cols-3 { grid-template-columns: repeat(3, 1fr); }
@media (max-width: 720px) {
  .grid.cols-2, .grid.cols-3 { grid-template-columns: 1fr; }
}

.week-card {
  position: relative; overflow: hidden;
  background: linear-gradient(180deg, rgba(255,255,255,.03), rgba(255,255,255,0));
  border: 1px solid rgba(255,255,255,.06);
  border-radius: var(--radius);
  padding: 18px;
  cursor: pointer;
  transition: transform .12s ease, border-color .2s ease;
}
.week-card:hover { transform: translateY(-2px); border-color: rgba(255,255,255,.18); }
.week-card .title { font-weight: 700; margin-bottom: 4px; }
.week-card .meta { font-size: 13px; color: var(--muted); }
.week-card .badge {
  position: absolute; top: 12px; right: 12px;
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: .4px;
  padding: 4px 8px; border-radius: 999px; background: rgba(255,255,255,.08);
}
.week-card.completed .badge { background: rgba(52,211,153,.15); color: var(--success); }

.flashcard {
  min-height: 220px; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 14px;
  text-align: center;
}
.flashcard .front { font-size: 32px; font-weight: 800; }
.flashcard .back { font-size: 22px; color: var(--muted); }

.choices { display: flex; flex-wrap: wrap; gap: 10px; justify-content: center; }
.choice {
  background: rgba(255,255,255,.06); border: 1px solid rgba(255,255,255,.08);
  border-radius: 10px; padding: 10px 14px; cursor: pointer; transition: background .15s ease;
}
.choice:hover { background: rgba(255,255,255,.12); }

.exercise .prompt { font-size: 18px; margin-bottom: 14px; }
.exercise .input {
  width: 100%; padding: 12px; border-radius: 10px; border: 1px solid rgba(255,255,255,.12);
  background: rgba(0,0,0,.25); color: var(--text); font-size: 16px;
}
.exercise .result { margin-top: 10px; font-weight: 700; }
.exercise .result.correct { color: var(--success); }
.exercise .result.incorrect { color: var(--danger); }

.login {
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  min-height: 60vh; gap: 18px; text-align: center;
}
.login h1 { font-size: 32px; }

.denied { text-align: center; padding: 40px 20px; }

.small { font-size: 12px; color: var(--muted); }

.progress-bar {
  width: 100%; height: 8px; background: rgba(255,255,255,.08); border-radius: 999px; overflow: hidden;
}
.progress-bar > i { display: block; height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent2)); border-radius: 999px; transition: width .4s ease; }