:root {
  --bg: #fdf4ff;
  --bg-card: #ffffff;
  --bg-input: #fbf7ff;
  --text: #4a3f55;
  --muted: #9b8aa8;
  --primary: #c3aed6;        /* pastel lavender */
  --primary-hover: #b49bce;
  --secondary: #a8d8ea;      /* pastel sky blue */
  --secondary-hover: #93cde3;
  --accent: #ffd6e8;         /* pastel pink */
  --success: #b5e7c7;        /* pastel mint */
  --success-ink: #4f9b6f;
  --danger: #ffb3ba;         /* pastel rose */
  --danger-ink: #c76872;
  --warn: #ffe0ac;           /* pastel peach */
  --warn-ink: #d29a52;
  --border: #efe4f5;
  --ghost-bg: #fbf7ff;
  --ghost-hover: #f3ecfa;
  --review-bg: #fff6f8;
  --pill-grad: linear-gradient(135deg, #f3e6fb, #e6f2fe);
  --pill-ink: #6a5a7a;
  --btn-ink: #4a3f55;
  --bg-wash:
    radial-gradient(900px 500px at 15% -5%, #e8f3ff 0%, transparent 60%),
    radial-gradient(900px 500px at 100% 0%, #ffe9f4 0%, transparent 55%),
    radial-gradient(1000px 700px at 50% 110%, #eafbf1 0%, transparent 60%);
  --radius: 18px;
  --shadow: 0 12px 30px rgba(170, 140, 200, 0.18);
}

/* Dark palette — applied when the user picks dark, or (no explicit
   choice) when the OS prefers dark. */
:root[data-theme="dark"] {
  --bg: #1b1824;
  --bg-card: #262232;
  --bg-input: #201c2b;
  --text: #ece6f2;
  --muted: #a99fb8;
  --primary: #a78fc4;
  --primary-hover: #b7a3d2;
  --secondary: #7fbdd6;
  --secondary-hover: #93cde3;
  --accent: #e0a6c4;
  --success: #8fcfa8;
  --success-ink: #a7e6c0;
  --danger: #e59aa2;
  --danger-ink: #f2b3ba;
  --warn: #e6c48a;
  --warn-ink: #f0d6a0;
  --border: #3a3448;
  --ghost-bg: #2d2838;
  --ghost-hover: #352f44;
  --review-bg: #2f2530;
  --pill-grad: linear-gradient(135deg, #3a3350, #2f3a4a);
  --pill-ink: #d6cce6;
  --btn-ink: #211d2b;
  --bg-wash:
    radial-gradient(900px 500px at 15% -5%, #24314a 0%, transparent 60%),
    radial-gradient(900px 500px at 100% 0%, #3a2436 0%, transparent 55%),
    radial-gradient(1000px 700px at 50% 110%, #1f3a2c 0%, transparent 60%);
  --shadow: 0 12px 30px rgba(0, 0, 0, 0.45);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #1b1824;
    --bg-card: #262232;
    --bg-input: #201c2b;
    --text: #ece6f2;
    --muted: #a99fb8;
    --primary: #a78fc4;
    --primary-hover: #b7a3d2;
    --secondary: #7fbdd6;
    --secondary-hover: #93cde3;
    --accent: #e0a6c4;
    --success: #8fcfa8;
    --success-ink: #a7e6c0;
    --danger: #e59aa2;
    --danger-ink: #f2b3ba;
    --warn: #e6c48a;
    --warn-ink: #f0d6a0;
    --border: #3a3448;
    --ghost-bg: #2d2838;
    --ghost-hover: #352f44;
    --review-bg: #2f2530;
    --pill-grad: linear-gradient(135deg, #3a3350, #2f3a4a);
    --pill-ink: #d6cce6;
    --btn-ink: #211d2b;
    --bg-wash:
      radial-gradient(900px 500px at 15% -5%, #24314a 0%, transparent 60%),
      radial-gradient(900px 500px at 100% 0%, #3a2436 0%, transparent 55%),
      radial-gradient(1000px 700px at 50% 110%, #1f3a2c 0%, transparent 60%);
    --shadow: 0 12px 30px rgba(0, 0, 0, 0.45);
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  background: var(--bg-wash), var(--bg);
  color: var(--text);
  transition: background 0.3s ease, color 0.3s ease;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.app-header {
  text-align: center;
  margin: 2.2rem 1rem 1rem;
}
.logo {
  font-size: clamp(2rem, 6vw, 3rem);
  margin: 0;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(90deg, #b49bce, #88c6e0 45%, #f49ec4);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  cursor: pointer;
  user-select: none;
}
.tagline { color: var(--muted); margin: 0.3rem 0 0; }

#app { width: 100%; max-width: 640px; padding: 0 1rem 3rem; }

.screen { display: none; }
.screen.active { display: block; animation: fade 0.25s ease; }
@keyframes fade { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; } }

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.6rem;
  box-shadow: var(--shadow);
  transition: background 0.3s ease, border-color 0.3s ease;
}

.theme-toggle {
  position: fixed;
  top: 1rem;
  right: 1rem;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  font-size: 1.3rem;
  line-height: 1;
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: transform 0.15s ease, background 0.3s ease;
  z-index: 10;
}
.theme-toggle:hover { transform: scale(1.08) rotate(-8deg); }
.card h2 { margin-top: 0; }

/* Buttons */
.btn {
  font: inherit;
  font-weight: 700;
  border: none;
  border-radius: 12px;
  padding: 0.85rem 1.1rem;
  cursor: pointer;
  color: var(--btn-ink);
  box-shadow: 0 4px 12px rgba(170, 140, 200, 0.18);
  transition: transform 0.08s ease, background 0.15s ease, box-shadow 0.15s, opacity 0.15s;
}
.btn:hover { transform: translateY(-1px); box-shadow: 0 7px 16px rgba(170, 140, 200, 0.26); }
.btn:active { transform: translateY(1px); box-shadow: 0 2px 8px rgba(170, 140, 200, 0.18); }
.btn-block { display: block; width: 100%; margin-top: 0.9rem; }
.btn-primary { background: var(--primary); }
.btn-primary:hover { background: var(--primary-hover); }
.btn-secondary { background: var(--secondary); }
.btn-secondary:hover { background: var(--secondary-hover); }
.btn-ghost { background: var(--ghost-bg); border: 1px solid var(--border); color: var(--text); box-shadow: none; }
.btn-ghost:hover { background: var(--ghost-hover); }
.btn-danger { background: var(--danger); }
.btn-danger:hover { filter: brightness(0.97); }
.btn .sub { display: block; font-weight: 400; font-size: 0.78rem; opacity: 0.85; margin-top: 0.15rem; }

/* Difficulty segmented control */
.segmented {
  display: flex;
  gap: 0.4rem;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 0.35rem;
}
.segmented button {
  flex: 1;
  font: inherit;
  font-weight: 700;
  color: var(--muted);
  background: transparent;
  border: none;
  border-radius: 9px;
  padding: 0.6rem 0.4rem;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, box-shadow 0.2s;
}
.segmented button.selected {
  background: var(--primary);
  color: var(--btn-ink);
  box-shadow: 0 3px 10px rgba(170, 140, 200, 0.25);
}
.diff-desc { color: var(--muted); font-size: 0.9rem; margin: 0.6rem 0 0; min-height: 1.2rem; }
.mode-heading { margin-top: 1.6rem; }

.category-block {
  margin-top: 1.6rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--border);
}
.category-block label { display: block; margin-bottom: 0.5rem; color: var(--muted); font-weight: 600; }
select {
  width: 100%;
  font: inherit;
  padding: 0.7rem;
  border-radius: 10px;
  background: var(--bg-input);
  color: var(--text);
  border: 1px solid var(--border);
}

/* Quiz */
.quiz-top { display: flex; align-items: center; justify-content: space-between; margin-bottom: 1.2rem; }
.progress-label { color: var(--muted); font-weight: 600; }

.timer { position: relative; width: 56px; height: 56px; }
.timer-ring { width: 56px; height: 56px; transform: rotate(-90deg); }
.timer-track { fill: none; stroke: var(--border); stroke-width: 5; }
.timer-progress {
  fill: none;
  stroke: var(--success);
  stroke-width: 5;
  stroke-linecap: round;
  stroke-dasharray: 125.6;
  stroke-dashoffset: 0;
  transition: stroke-dashoffset 1s linear, stroke 0.3s;
}
.timer-progress.low { stroke: var(--warn); }
.timer-progress.critical { stroke: var(--danger); }
.timer-text {
  position: absolute; inset: 0;
  display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 1.05rem;
}

.prompt-label { color: var(--muted); text-transform: uppercase; letter-spacing: 0.08em; font-size: 0.75rem; margin-bottom: 0.3rem; }

.word-bank {
  list-style: none;
  margin: 0 0 1.4rem;
  padding: 0.7rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 10px;
}
.word-bank li {
  padding: 0.3rem 0.7rem;
  border-radius: 999px;
  background: var(--pill-grad);
  border: 1px solid var(--border);
  color: var(--pill-ink);
  font-size: 0.9rem;
  font-weight: 600;
  transition: background 0.15s, color 0.15s, transform 0.1s;
}
/* Easy mode: pills become clickable answer buttons */
.word-bank.clickable li {
  cursor: pointer;
  padding: 0.5rem 0.95rem;
  font-size: 1rem;
}
.word-bank.clickable li:hover { background: var(--primary); color: var(--btn-ink); transform: translateY(-1px); }
.word-bank.clickable li:active { transform: translateY(0); }
.definition { font-size: 1.3rem; line-height: 1.5; margin: 0 0 1.4rem; min-height: 3rem; }

#answerForm { display: flex; gap: 0.6rem; }
#answerInput {
  flex: 1;
  font: inherit;
  font-size: 1.1rem;
  padding: 0.8rem 1rem;
  border-radius: 10px;
  background: var(--bg-input);
  color: var(--text);
  border: 2px solid var(--border);
}
#answerInput:focus { outline: none; border-color: var(--primary-hover); }

.feedback { min-height: 1.5rem; margin-top: 1rem; font-weight: 600; }
.feedback.correct { color: var(--success-ink); }
.feedback.wrong { color: var(--danger-ink); }

/* Results */
.score { font-size: 3rem; font-weight: 800; margin: 0.4rem 0 0; text-align: center; }
.score-sub { text-align: center; color: var(--muted); margin-top: 0.3rem; }
.review { margin: 1.4rem 0; }
.review-item {
  border: 1px solid var(--border);
  border-left: 4px solid var(--danger);
  border-radius: 12px;
  padding: 0.8rem 1rem;
  margin-bottom: 0.7rem;
  background: var(--review-bg);
}
.review-item .def { color: var(--text); margin: 0 0 0.5rem; font-weight: 600; }
.review-item .row { font-size: 0.92rem; margin: 0.15rem 0; }
.review-item .you { color: var(--danger-ink); }
.review-item .ans { color: var(--success-ink); }
.review-perfect { text-align: center; color: var(--success-ink); font-weight: 700; margin: 1.4rem 0; }

.actions { display: flex; flex-wrap: wrap; gap: 0.6rem; justify-content: center; margin-top: 1.2rem; }
.actions .btn { flex: 1 1 auto; }

/* Progress graph */
.graph-wrap { width: 100%; overflow-x: auto; }
.graph-wrap svg { display: block; width: 100%; height: auto; }
.graph-empty { color: var(--muted); text-align: center; padding: 2rem 0; }
.axis-line { stroke: var(--border); stroke-width: 1; }
.grid-line { stroke: var(--border); stroke-width: 1; stroke-dasharray: 3 4; opacity: 0.5; }
.axis-text { fill: var(--muted); font-size: 11px; }
.data-line { fill: none; stroke: var(--primary-hover); stroke-width: 2.5; }
.data-point { fill: var(--secondary); stroke: var(--bg-card); stroke-width: 2; }