:root {
  --bg: #f6f7fb; --card: #fff; --text: #282e3e; --muted: #646f90; --line: #d9dde8;
  --primary: #4255ff; --primary-d: #2e3ad6; --ok: #18ae79; --ok-bg: #e5f8f0; --bad: #e2364b; --bad-bg: #fdecee;
  --warn: #ffcd1f; --radius: 14px; --shadow: 0 2px 8px rgba(40, 46, 62, .08);
}
@media (prefers-color-scheme: dark) {
  :root { --bg: #0a092d; --card: #2e3856; --text: #f6f7fb; --muted: #a8b1cc; --line: #4b5578;
    --ok-bg: #12382f; --bad-bg: #44202a; --shadow: 0 2px 8px rgba(0, 0, 0, .35); }
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body { font: 16px/1.45 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; background: var(--bg); color: var(--text); min-height: 100vh; }
a { color: var(--primary); }
.top { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: .7rem 1.2rem;
  background: var(--card); box-shadow: var(--shadow); position: sticky; top: 0; z-index: 5; }
.brand { display: flex; align-items: center; gap: .5rem; font-weight: 700; font-size: 1.15rem; color: var(--text); text-decoration: none; }
#nav { display: flex; gap: .5rem; align-items: center; flex-wrap: wrap; }
main { max-width: 900px; margin: 0 auto; padding: 1.5rem 1rem 4rem; }
h1 { font-size: 1.7rem; margin: .2rem 0 1rem; }
h2 { font-size: 1.2rem; margin: 1.5rem 0 .7rem; }
.muted { color: var(--muted); }
.center { text-align: center; }
.row { display: flex; gap: .6rem; align-items: center; flex-wrap: wrap; }
.spacer { flex: 1; }

button, .btn { font: inherit; border: 2px solid var(--line); background: var(--card); color: var(--text); border-radius: 10px;
  padding: .5rem 1rem; cursor: pointer; font-weight: 600; text-decoration: none; display: inline-flex; align-items: center; gap: .4rem; }
button:hover, .btn:hover { border-color: var(--primary); }
button.primary, .btn.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
button.primary:hover, .btn.primary:hover { background: var(--primary-d); }
button.danger { color: var(--bad); }
button.small, .btn.small { padding: .25rem .65rem; font-size: .9rem; }
button:disabled { opacity: .5; cursor: default; }
input, textarea, select { font: inherit; color: var(--text); background: var(--card); border: 2px solid var(--line);
  border-radius: 10px; padding: .55rem .75rem; width: 100%; }
input:focus, textarea:focus, select:focus { outline: none; border-color: var(--primary); }
textarea { resize: vertical; min-height: 2.6rem; }
label { font-weight: 600; font-size: .9rem; color: var(--muted); display: block; margin: .8rem 0 .3rem; }

.panel { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1.3rem; }
.login { max-width: 380px; margin: 3rem auto; }
.error { color: var(--bad); margin-top: .7rem; min-height: 1.2em; }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 1rem; }
.setcard { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1rem 1.2rem; cursor: pointer;
  border-bottom: 4px solid transparent; text-decoration: none; color: var(--text); display: block; }
.setcard:hover { border-bottom-color: var(--primary); }
.setcard h3 { margin: 0 0 .3rem; font-size: 1.1rem; overflow-wrap: anywhere; }
.pill { display: inline-block; background: var(--bg); border-radius: 99px; padding: .1rem .6rem; font-size: .8rem; font-weight: 600; color: var(--muted); }
.bar { height: 6px; border-radius: 3px; background: var(--line); overflow: hidden; margin-top: .7rem; }
.bar > i { display: block; height: 100%; background: var(--ok); }

.modes { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: .7rem; margin: 1rem 0 1.5rem; }
.mode { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: .9rem 1rem; display: flex; align-items: center;
  gap: .6rem; font-weight: 700; color: var(--text); text-decoration: none; border-bottom: 4px solid transparent; }
.mode:hover { border-bottom-color: var(--primary); }
.mode .ic { font-size: 1.4rem; }

.termlist { display: flex; flex-direction: column; gap: .5rem; }
.term { background: var(--card); border-radius: 10px; box-shadow: var(--shadow); padding: .8rem 1rem; display: grid;
  grid-template-columns: 1fr 2fr auto; gap: 1rem; align-items: start; }
.term .t { font-weight: 600; border-right: 2px solid var(--bg); padding-right: 1rem; }
.term .t, .term .d { white-space: pre-wrap; overflow-wrap: anywhere; }
.star { border: none; background: none; padding: 0 .2rem; font-size: 1.2rem; color: var(--line); }
.star.on { color: var(--warn); }
@media (max-width: 600px) { .term { grid-template-columns: 1fr auto; } .term .d { grid-column: 1; } .term .t { border: none; } }

/* editor */
.edrow { background: var(--card); border-radius: 10px; box-shadow: var(--shadow); padding: .8rem 1rem; margin-bottom: .6rem; }
.edrow .hd { display: flex; justify-content: space-between; align-items: center; color: var(--muted); font-weight: 700; font-size: .9rem; }
.edrow .cols { display: grid; grid-template-columns: 1fr 1fr; gap: .8rem; margin-top: .4rem; }
.edrow .cols small { color: var(--muted); font-size: .75rem; text-transform: uppercase; letter-spacing: .04em; }
@media (max-width: 600px) { .edrow .cols { grid-template-columns: 1fr; } }
.sticky-actions { position: sticky; bottom: 0; background: var(--bg); padding: .8rem 0; display: flex; gap: .6rem; justify-content: flex-end; }

/* flashcards */
.flip { perspective: 1400px; height: min(55vh, 380px); margin: 1rem 0; cursor: pointer; user-select: none; }
.flip-inner { position: relative; width: 100%; height: 100%; transition: transform .45s; transform-style: preserve-3d; }
.flip.flipped .flip-inner { transform: rotateY(180deg); }
.face { position: absolute; inset: 0; backface-visibility: hidden; background: var(--card); border-radius: var(--radius);
  box-shadow: 0 4px 16px rgba(40, 46, 62, .15); display: flex; align-items: center; justify-content: center; padding: 2rem;
  font-size: clamp(1.2rem, 3.5vw, 2rem); text-align: center; white-space: pre-wrap; overflow: auto; overflow-wrap: anywhere; }
.face.back { transform: rotateY(180deg); }
.face .lbl { position: absolute; top: .8rem; left: 1rem; font-size: .8rem; color: var(--muted); font-weight: 700; }
.fc-ctrl { display: flex; justify-content: center; align-items: center; gap: 1rem; }
.fc-ctrl .count { min-width: 5rem; text-align: center; font-weight: 700; }

/* learn / test */
.q { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1.5rem; margin: 1rem 0; }
.q .prompt { font-size: 1.35rem; white-space: pre-wrap; overflow-wrap: anywhere; margin: .5rem 0 1.3rem; }
.q .kind { color: var(--muted); font-size: .85rem; font-weight: 700; }
.choices { display: grid; grid-template-columns: 1fr 1fr; gap: .7rem; }
@media (max-width: 600px) { .choices { grid-template-columns: 1fr; } }
.choice { text-align: left; justify-content: flex-start; padding: .8rem 1rem; white-space: pre-wrap; overflow-wrap: anywhere; font-weight: 500; }
.choice .n { color: var(--muted); font-weight: 700; margin-right: .3rem; }
.choice.correct { border-color: var(--ok); background: var(--ok-bg); }
.choice.wrong { border-color: var(--bad); background: var(--bad-bg); }
.feedback { margin-top: 1rem; padding: .8rem 1rem; border-radius: 10px; white-space: pre-wrap; overflow-wrap: anywhere; }
.feedback.ok { background: var(--ok-bg); color: var(--ok); font-weight: 700; }
.feedback.bad { background: var(--bad-bg); }
.feedback.bad b { color: var(--bad); }
.progress { display: flex; gap: .5rem; align-items: center; }
.progress .bar { flex: 1; margin: 0; height: 10px; border-radius: 5px; }
.result-big { font-size: 3rem; font-weight: 800; color: var(--primary); }
.settings { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: .3rem 1rem; }
.check { display: flex; gap: .5rem; align-items: center; font-weight: 500; color: var(--text); }
.check input { width: auto; }

/* match */
.match { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: .7rem; margin-top: 1rem; }
.tile { min-height: 110px; background: var(--card); border: 2px solid var(--line); border-radius: 12px; padding: .7rem; display: flex;
  align-items: center; justify-content: center; text-align: center; cursor: pointer; overflow-wrap: anywhere; font-weight: 500; transition: opacity .3s, transform .3s; }
.tile.sel { border-color: var(--primary); background: #e8ebff; color: #282e3e; }
.tile.bad { border-color: var(--bad); background: var(--bad-bg); }
.tile.gone { opacity: 0; transform: scale(.85); pointer-events: none; }
.timer { font-size: 1.4rem; font-weight: 800; font-variant-numeric: tabular-nums; }

#toast { position: fixed; bottom: 1.2rem; left: 50%; transform: translateX(-50%) translateY(calc(100% + 2rem)); visibility: hidden; background: #282e3e; color: #fff;
  padding: .6rem 1.1rem; border-radius: 10px; transition: transform .25s; z-index: 50; max-width: 90vw; }
#toast.show { transform: translateX(-50%) translateY(0); visibility: visible; }
.kbd { font-size: .8rem; color: var(--muted); text-align: center; margin-top: .6rem; }
@media (max-width: 500px) { .hide-sm { display: none; } main { padding-top: 1rem; } }