:root {
  --bg: #0a0e27;
  --surface: #141a3a;
  --surface-2: #1e2650;
  --border: #2a3270;
  --text: #e8ecf7;
  --text-dim: #9aa3c7;
  --accent: #4255ff;
  --accent-hover: #5a6bff;
  --success: #22c55e;
  --danger: #ef4444;
  --warning: #f59e0b;
  --shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
  --radius: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  min-height: 100vh;
  line-height: 1.5;
}

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

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 10;
}

.topbar .brand {
  font-size: 20px;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
}

.topbar .brand .q { color: var(--accent); }

.topbar .right {
  display: flex;
  align-items: center;
  gap: 12px;
}

.user-chip {
  color: var(--text-dim);
  font-size: 14px;
}

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

.container-narrow {
  max-width: 720px;
  margin: 0 auto;
  padding: 24px;
}

h1 { font-size: 28px; margin: 0 0 16px; }
h2 { font-size: 22px; margin: 0 0 12px; }
h3 { font-size: 18px; margin: 0 0 10px; }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 16px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  text-decoration: none;
}

.btn:hover { background: var(--border); text-decoration: none; }

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}
.btn-primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); }

.btn-danger {
  background: transparent;
  border-color: var(--danger);
  color: var(--danger);
}
.btn-danger:hover { background: rgba(239, 68, 68, 0.12); }

.btn-ghost {
  background: transparent;
  border-color: transparent;
  color: var(--text-dim);
}
.btn-ghost:hover { color: var(--text); background: var(--surface-2); }

.btn-sm { padding: 6px 10px; font-size: 13px; }

input[type="text"],
input[type="password"],
textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font-size: 14px;
  font-family: inherit;
}

input:focus, textarea:focus {
  outline: none;
  border-color: var(--accent);
}

textarea { resize: vertical; min-height: 60px; }

.form-row { margin-bottom: 14px; }
.form-row label {
  display: block;
  font-size: 13px;
  color: var(--text-dim);
  margin-bottom: 6px;
  font-weight: 500;
}

.alert {
  padding: 12px 16px;
  border-radius: 8px;
  margin-bottom: 16px;
  font-size: 14px;
}
.alert-error { background: rgba(239, 68, 68, 0.12); border: 1px solid var(--danger); color: #fca5a5; }
.alert-info  { background: rgba(66, 85, 255, 0.12); border: 1px solid var(--accent); color: #b8c2ff; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.set-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  position: relative;
  transition: transform 0.15s, border-color 0.15s;
  display: flex;
  flex-direction: column;
  min-height: 140px;
  color: var(--text);
  text-decoration: none;
}

.set-card:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
  text-decoration: none;
}

.set-card .color-bar {
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 4px;
  border-top-left-radius: var(--radius);
  border-top-right-radius: var(--radius);
}

.set-card h3 { margin: 8px 0 6px; font-size: 17px; color: var(--text); }
.set-card .desc { color: var(--text-dim); font-size: 13px; flex: 1; }
.set-card .meta { margin-top: 12px; font-size: 12px; color: var(--text-dim); display: flex; justify-content: space-between; }

.set-actions {
  position: absolute;
  top: 10px;
  right: 10px;
  display: flex;
  gap: 4px;
  opacity: 0;
  transition: opacity 0.15s;
}
.set-card:hover .set-actions { opacity: 1; }

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-dim);
}

.hero {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 24px;
}

.mode-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
  margin-top: 16px;
}

.mode-btn {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px 14px;
  text-align: center;
  color: var(--text);
  text-decoration: none;
  transition: background 0.15s, border-color 0.15s;
}
.mode-btn:hover { background: var(--border); border-color: var(--accent); text-decoration: none; }
.mode-btn .icon { font-size: 28px; display: block; margin-bottom: 4px; }
.mode-btn .label { font-weight: 600; font-size: 14px; }
.mode-btn .sub { font-size: 12px; color: var(--text-dim); margin-top: 2px; }

/* ── Login ── */
.login-wrap {
  min-height: calc(100vh - 60px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.login-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  width: 100%;
  max-width: 380px;
  box-shadow: var(--shadow);
}
.login-box h1 { text-align: center; }
.login-box .sub { text-align: center; color: var(--text-dim); margin-bottom: 24px; }

/* ── Editor ── */
.card-row {
  display: grid;
  grid-template-columns: 40px 1fr 1fr 40px;
  gap: 12px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  margin-bottom: 10px;
  align-items: flex-start;
}
.card-row .idx { color: var(--text-dim); font-weight: 600; padding-top: 10px; text-align: center; }
.card-row textarea { min-height: 48px; }
.card-row .drop {
  border: none;
  background: transparent;
  color: var(--text-dim);
  cursor: pointer;
  font-size: 18px;
  padding: 4px;
}
.card-row .drop:hover { color: var(--danger); }

/* ── Flashcards ── */
.flashcard {
  perspective: 1200px;
  width: 100%;
  max-width: 640px;
  height: 360px;
  margin: 32px auto;
  cursor: pointer;
}
.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 0.55s cubic-bezier(.3, 0, .25, 1);
  transform-style: preserve-3d;
}
.flashcard.flipped .flashcard-inner { transform: rotateY(180deg); }
.flashcard-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-size: 24px;
  line-height: 1.4;
  overflow: auto;
}
.flashcard-face.back { transform: rotateY(180deg); color: var(--text-dim); font-size: 20px; }

.flashcard-ctrls {
  display: flex;
  justify-content: center;
  gap: 14px;
  align-items: center;
  margin-top: 12px;
}
.flashcard-ctrls .count {
  color: var(--text-dim);
  font-size: 14px;
  min-width: 80px;
  text-align: center;
}

/* ── Learn ── */
.learn-wrap { max-width: 720px; margin: 0 auto; }
.progress-bar {
  height: 8px;
  background: var(--surface);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: 24px;
}
.progress-bar-fill {
  height: 100%;
  background: var(--accent);
  transition: width 0.4s ease;
}
.learn-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px;
}
.prompt-label { color: var(--text-dim); font-size: 12px; text-transform: uppercase; letter-spacing: 0.6px; margin-bottom: 8px; }
.prompt-text { font-size: 22px; margin-bottom: 20px; }
.choices {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}
.choice {
  padding: 14px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  text-align: left;
  cursor: pointer;
  font-size: 15px;
  transition: border-color 0.15s, background 0.15s;
}
.choice:hover:not(:disabled) { border-color: var(--accent); }
.choice.correct { border-color: var(--success); background: rgba(34, 197, 94, 0.15); }
.choice.wrong   { border-color: var(--danger); background: rgba(239, 68, 68, 0.15); }
.choice:disabled { cursor: default; }

.written-answer {
  display: flex;
  gap: 10px;
}
.feedback {
  margin-top: 14px;
  padding: 10px 14px;
  border-radius: 8px;
  font-size: 14px;
}
.feedback.correct { background: rgba(34, 197, 94, 0.12); border: 1px solid var(--success); }
.feedback.wrong   { background: rgba(239, 68, 68, 0.12); border: 1px solid var(--danger); }

/* ── Test ── */
.test-q {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 14px;
}
.test-q .num { color: var(--text-dim); font-size: 13px; font-weight: 600; margin-bottom: 6px; }
.test-q .q { font-size: 17px; margin-bottom: 12px; }
.test-q .result-row { margin-top: 8px; font-size: 14px; color: var(--text-dim); }
.test-q.correct { border-color: var(--success); }
.test-q.wrong   { border-color: var(--danger); }

/* ── Match ── */
.match-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  margin-top: 20px;
}
@media (max-width: 600px) {
  .match-grid { grid-template-columns: repeat(2, 1fr); }
  .choices    { grid-template-columns: 1fr; }
}
.match-tile {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px;
  min-height: 90px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  font-size: 14px;
  transition: border-color 0.15s, background 0.15s, transform 0.2s;
}
.match-tile:hover:not(.gone):not(.selected) { border-color: var(--accent); }
.match-tile.selected { border-color: var(--accent); background: var(--surface-2); }
.match-tile.correct  { border-color: var(--success); background: rgba(34, 197, 94, 0.15); transform: scale(0.96); }
.match-tile.wrong    { border-color: var(--danger); background: rgba(239, 68, 68, 0.15); animation: shake 0.25s; }
.match-tile.gone     { opacity: 0; pointer-events: none; }
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25%      { transform: translateX(-6px); }
  75%      { transform: translateX(6px); }
}

/* ── Score screen ── */
.score-box {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 32px;
  text-align: center;
}
.score-big { font-size: 48px; font-weight: 700; color: var(--accent); }

/* ── Modal ── */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
}
.modal {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  width: 100%;
  max-width: 420px;
  box-shadow: var(--shadow);
}
.modal h2 { margin-top: 0; }
.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  margin-top: 20px;
}

.row-flex { display: flex; align-items: center; gap: 12px; }
.spacer { flex: 1; }
.muted { color: var(--text-dim); }

.hidden { display: none !important; }