:root {
  --bg: #ffffff;
  --bg-soft: #f4f5f7;
  --fg: #16181d;
  --fg-soft: #6b7280;
  --line: rgba(0, 0, 0, 0.1);
  --accent: #4f46e5;
  --accent-soft: rgba(99, 102, 241, 0.12);
  --ok: #16a34a;
  --no: #dc2626;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14161b;
    --bg-soft: #1d2027;
    --fg: #e8eaf0;
    --fg-soft: #9aa0ad;
    --line: rgba(255, 255, 255, 0.12);
    --accent: #a5b4fc;
    --accent-soft: rgba(129, 140, 248, 0.18);
  }
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body { margin: 0; height: 100%; }
body {
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, 'Pretendard', 'Apple SD Gothic Neo', 'Segoe UI', sans-serif;
  color: var(--fg);
  background: var(--bg);
  display: flex;
  flex-direction: column;
  padding-bottom: env(safe-area-inset-bottom);
}
header {
  position: sticky; top: 0; z-index: 5;
  display: flex; align-items: center; gap: 8px;
  padding: max(10px, env(safe-area-inset-top)) 16px 10px;
  background: var(--bg); border-bottom: 1px solid var(--line);
}
header .brand { font-weight: 800; letter-spacing: -0.02em; }
header .badge { margin-left: auto; }
.badge { font-size: 12px; color: var(--fg-soft); border: 1px solid var(--line); border-radius: 999px; padding: 2px 9px; }
main { flex: 1; padding: 16px; max-width: 640px; width: 100%; margin: 0 auto; }
section { display: none; }
section.on { display: block; }

nav {
  position: sticky; bottom: 0; display: grid; grid-template-columns: repeat(4, 1fr);
  background: var(--bg); border-top: 1px solid var(--line);
  padding-bottom: env(safe-area-inset-bottom);
}
nav button {
  border: 0; background: transparent; color: var(--fg-soft);
  padding: 12px 4px 14px; font: inherit; font-size: 13px; cursor: pointer;
}
nav button.on { color: var(--accent); font-weight: 700; }

button, input, textarea, select {
  font: inherit; color: var(--fg); border-radius: 12px;
}
button { border: 1px solid var(--line); background: var(--bg-soft); padding: 11px 14px; cursor: pointer; }
button.primary { background: var(--accent); color: #fff; border-color: transparent; font-weight: 700; }
button.ghost { background: transparent; border-color: transparent; color: var(--fg-soft); }
button:active { transform: translateY(1px); }
input, textarea, select { width: 100%; background: var(--bg); border: 1px solid var(--line); padding: 11px 12px; }
textarea { min-height: 88px; resize: vertical; }

.row { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.row > .grow { flex: 1; }
.card { border: 1px solid var(--line); border-radius: 16px; padding: 16px; margin-bottom: 12px; }
.term { font-size: 26px; font-weight: 800; letter-spacing: -0.02em; word-break: break-word; }
.meta { display: flex; gap: 8px; align-items: center; color: var(--fg-soft); font-size: 13px; flex-wrap: wrap; margin-top: 2px; }
.pos { padding: 1px 8px; border-radius: 999px; background: var(--accent-soft); color: var(--accent); font-size: 12px; }
.ko { margin-top: 10px; font-size: 19px; font-weight: 700; word-break: keep-all; }
.ko.sentence { font-size: 17px; font-weight: 600; }
.defs { margin: 10px 0 0; padding-left: 18px; color: var(--fg-soft); font-size: 14px; }
.ex { margin-top: 10px; padding: 10px 12px; border-radius: 12px; background: var(--bg-soft); font-size: 14px; font-style: italic; }
.exko { margin-top: 5px; font-style: normal; font-size: 13px; color: var(--fg-soft); }
.tag { margin-left: 6px; font-style: normal; font-size: 11px; opacity: 0.55; }
.foot { margin-top: 10px; font-size: 12px; color: var(--fg-soft); }
.actions { display: flex; gap: 8px; margin-top: 12px; }
.actions button { flex: 1; }
.hint { color: var(--fg-soft); font-size: 13px; }
.empty { color: var(--fg-soft); text-align: center; padding: 40px 12px; line-height: 1.9; }
.err { color: var(--no); }

.wordrow { display: flex; gap: 10px; align-items: flex-start; padding: 12px 0; border-bottom: 1px solid var(--line); }
.wordrow .w { font-weight: 700; }
.wordrow .g { color: var(--fg-soft); font-size: 14px; }
.wordrow .right { margin-left: auto; display: flex; gap: 6px; align-items: center; }
.wordrow button { padding: 6px 10px; font-size: 13px; }

.choices { display: grid; gap: 8px; margin-top: 14px; }
.choices button { text-align: left; }
.choices button.right { border-color: var(--ok); color: var(--ok); font-weight: 700; }
.choices button.wrong { border-color: var(--no); color: var(--no); }
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-bottom: 14px; }
.stat { background: var(--bg-soft); border-radius: 12px; padding: 10px 6px; text-align: center; }
.stat b { display: block; font-size: 19px; }
.stat span { font-size: 11px; color: var(--fg-soft); }
fieldset { border: 1px solid var(--line); border-radius: 14px; padding: 14px; margin: 0 0 14px; }
legend { font-weight: 700; padding: 0 6px; }
.field { display: grid; gap: 6px; margin-bottom: 12px; }
.field label { font-size: 14px; font-weight: 600; }
code { background: var(--bg-soft); padding: 1px 6px; border-radius: 6px; font-size: 13px; }
.skel { height: 16px; border-radius: 8px; background: var(--bg-soft); margin-top: 10px; animation: pulse 1s ease-in-out infinite; }
@keyframes pulse { 50% { opacity: 0.45; } }