:root {
  --bg: #0f1419;
  --panel: #1a2029;
  --panel-2: #232c38;
  --text: #e6edf3;
  --muted: #8b97a7;
  --accent: #ffb454;
  --accent-2: #4a9eff;
  --green: #3fb950;
  --red: #f85149;
  --border: #2d3744;
  --radius: 14px;
  font-size: 16px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 22px;
  padding-top: calc(14px + env(safe-area-inset-top));
  padding-left: calc(22px + env(safe-area-inset-left));
  padding-right: calc(22px + env(safe-area-inset-right));
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  gap: 10px;
  position: sticky;
  top: 0;
  background: var(--bg);
  z-index: 10;
}
header h1 { font-size: 1.15rem; margin: 0; letter-spacing: 0.3px; }

nav { display: flex; gap: 6px; }
.nav-btn {
  background: transparent;
  color: var(--muted);
  border: 1px solid transparent;
  padding: 7px 14px;
  border-radius: 9px;
  cursor: pointer;
  font-size: 0.92rem;
}
.nav-btn:hover { color: var(--text); background: var(--panel); }
.nav-btn.active { color: var(--accent); background: var(--panel); border-color: var(--border); }

main {
  flex: 1;
  width: 100%;
  max-width: 720px;
  margin: 0 auto;
  padding: 26px 18px;
}

.hidden { display: none !important; }
.muted { color: var(--muted); font-size: 0.85rem; }

/* ---- study ---- */
.study-progress {
  display: flex;
  justify-content: space-between;
  color: var(--muted);
  font-size: 0.85rem;
  margin-bottom: 14px;
}
#due-count { color: var(--accent); font-weight: 600; }

.card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px 28px;
  min-height: 230px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  cursor: pointer;
  transition: border-color 0.15s;
}
.card:hover { border-color: #3a4a5a; }
.card-pos {
  position: relative;
  top: -14px;
  color: var(--accent-2);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  height: 0;
}
.card-front {
  font-size: 2.4rem;
  font-weight: 600;
  text-align: center;
  word-break: break-word;
}

.card-back {
  margin-top: 26px;
  border-top: 1px dashed var(--border);
  padding-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.back-row { display: flex; flex-direction: column; gap: 3px; }
.back-row .label {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--muted);
}
#back-word { font-size: 1.5rem; font-weight: 600; color: var(--accent); }
#back-example-de { font-size: 1.05rem; font-style: italic; }
#back-example-en { font-size: 1rem; color: var(--muted); }

/* hover-to-align example words */
.de-word { cursor: help; border-radius: 4px; padding: 0 1px; transition: background 0.1s; }
.de-word:hover { background: rgba(74, 158, 255, 0.22); }
.de-word.active { background: rgba(74, 158, 255, 0.32); }
.de-word.no-match { background: rgba(139, 151, 167, 0.18); }
.en-word { border-radius: 4px; padding: 0 1px; transition: background 0.1s, color 0.1s; }
.en-word.hl { background: var(--accent-2); color: #04101f; }

#show-area { text-align: center; margin-top: 22px; }

button.primary {
  background: var(--accent);
  color: #1a1206;
  border: none;
  border-radius: 10px;
  padding: 12px 22px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
}
button.primary:hover { filter: brightness(1.08); }
button.big { width: 100%; padding: 16px; font-size: 1.1rem; }

button.secondary {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 22px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
}
button.secondary:hover:not(:disabled) { border-color: var(--accent-2); color: var(--accent-2); }
button.secondary:disabled { opacity: 0.4; cursor: not-allowed; }
.empty-actions { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }
.study-review-link { margin-left: auto; }

#grade-area {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin-top: 22px;
}
.grade {
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 6px;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  font-size: 0.95rem;
  font-weight: 600;
}
.grade:hover { border-color: var(--accent-2); }
.grade small { color: var(--muted); font-weight: 400; font-size: 0.72rem; }
.grade[data-grade="0"]:hover { border-color: var(--red); }
.grade[data-grade="5"]:hover { border-color: var(--green); }

kbd {
  background: #00000040;
  border: 1px solid var(--border);
  border-radius: 5px;
  padding: 1px 6px;
  font-size: 0.7rem;
  color: var(--muted);
}

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 38px 28px;
  text-align: center;
}
.panel h2 { margin-top: 0; }

/* ---- browse ---- */
.browse-controls {
  display: flex;
  gap: 10px;
  margin-bottom: 16px;
  align-items: center;
  flex-wrap: wrap;
}
#search {
  flex: 1;
  min-width: 180px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 10px 13px;
  color: var(--text);
  font-size: 0.95rem;
}
#filter-pos {
  background: var(--panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 10px;
}
.browse-row {
  display: grid;
  grid-template-columns: 1.4fr 1.4fr auto;
  gap: 12px;
  align-items: center;
  padding: 11px 14px;
  border-bottom: 1px solid var(--border);
}
.browse-row:hover { background: var(--panel); }
.bw-de { font-weight: 600; }
.bw-en { color: var(--muted); }
.bw-status {
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  padding: 3px 8px;
  border-radius: 20px;
  text-align: center;
}
.bw-status.new { background: #2d3744; color: var(--muted); }
.bw-status.learning { background: #3a2f1a; color: var(--accent); }
.bw-status.learned { background: #16321d; color: var(--green); }
.browse-more { padding: 16px; text-align: center; }

/* ---- stats ---- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-bottom: 22px;
}
.stat {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 12px;
  text-align: center;
}
.stat-num { font-size: 2rem; font-weight: 700; color: var(--accent); }
.stat-lbl { color: var(--muted); font-size: 0.8rem; margin-top: 4px; }
.stat-bar-wrap {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 20px;
  height: 28px;
  overflow: hidden;
  margin-bottom: 30px;
}
.stat-bar {
  background: linear-gradient(90deg, var(--green), #5fd97a);
  height: 100%;
  width: 0;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding-right: 12px;
  color: #07210d;
  font-size: 0.75rem;
  font-weight: 700;
  transition: width 0.4s;
  white-space: nowrap;
}
.danger-zone { text-align: center; }
#reset-btn {
  background: transparent;
  border: 1px solid var(--red);
  color: var(--red);
  padding: 9px 18px;
  border-radius: 9px;
  cursor: pointer;
}
#reset-btn:hover { background: var(--red); color: #fff; }

/* ---- similar tab ---- */
.seg {
  display: inline-flex;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 3px;
  gap: 3px;
}
.seg-btn {
  background: transparent;
  color: var(--muted);
  border: none;
  padding: 7px 14px;
  border-radius: 7px;
  cursor: pointer;
  font-size: 0.9rem;
}
.seg-btn.active { background: var(--panel-2); color: var(--accent); }
.similar-hint { margin: 0 0 16px; }

.sim-group {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  margin-bottom: 12px;
}
.sim-group-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 10px;
}
.sim-key { color: var(--accent); font-weight: 600; font-size: 1.05rem; }
.sim-drill-btn {
  margin-left: auto;
  background: var(--panel-2);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 12px;
  cursor: pointer;
  font-size: 0.85rem;
  white-space: nowrap;
}
.sim-drill-btn:hover { border-color: var(--accent-2); color: var(--accent-2); }
.sim-chips { display: flex; flex-wrap: wrap; gap: 7px; }
.sim-chip {
  padding: 5px 11px;
  border-radius: 20px;
  font-size: 0.92rem;
  border: 1px solid var(--border);
  background: var(--panel-2);
}
.sim-chip.learning { border-color: var(--accent); color: var(--accent); }
.sim-chip.learned { border-color: var(--green); color: var(--green); }

.link-btn {
  background: none;
  border: none;
  color: var(--accent-2);
  cursor: pointer;
  font-size: 0.9rem;
  padding: 0 0 12px;
}
.link-btn:hover { text-decoration: underline; }
.drill-peers #drill-peers { color: var(--accent-2); font-size: 0.95rem; }

footer {
  text-align: center;
  padding: 16px;
  padding-bottom: calc(16px + env(safe-area-inset-bottom));
  border-top: 1px solid var(--border);
}

@media (max-width: 560px) {
  :root { font-size: 15px; }
  header {
    padding: 11px 14px;
    /* keep clear of the status bar / Dynamic Island */
    padding-top: calc(11px + env(safe-area-inset-top));
    padding-left: calc(14px + env(safe-area-inset-left));
    padding-right: calc(14px + env(safe-area-inset-right));
  }
  header h1 { font-size: 1.05rem; width: 100%; text-align: center; }
  nav { width: 100%; justify-content: space-between; gap: 4px; }
  .nav-btn { flex: 1; padding: 9px 4px; font-size: 0.85rem; text-align: center; }

  main { padding: 16px 12px; }
  .card { padding: 30px 18px; min-height: 190px; }
  .card-front { font-size: 1.9rem; }

  /* bigger, finger-friendly controls */
  .grade { padding: 14px 4px; min-height: 52px; font-size: 1rem; }
  .grade small { display: none; }
  button.big { padding: 18px; }
  .empty-actions { flex-direction: column; }
  .empty-actions button { width: 100%; }

  .stats-grid { grid-template-columns: repeat(2, 1fr); }

  /* browse rows stack so English doesn't get crushed */
  .browse-row { grid-template-columns: 1fr auto; row-gap: 2px; }
  .bw-en { grid-column: 1; }
  .bw-status { grid-row: 1 / 3; grid-column: 2; align-self: center; }

  .browse-controls, .seg { width: 100%; }
  .seg { justify-content: space-between; }
  .seg-btn { flex: 1; }
  .sim-chips { gap: 6px; }

  kbd { display: none; } /* shortcuts are desktop-only */
}

/* Touch devices: hover styles can stick, and tap targets matter. */
@media (hover: none) {
  .de-word { cursor: pointer; padding: 1px 2px; } /* easier to tap */
}

/* Avoid the grey tap flash on iOS and stop double-tap zoom on controls. */
button, .de-word, .en-word, .nav-btn, .seg-btn, .sim-chip {
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}