:root {
  --bg: #0f1420;
  --panel: #182031;
  --panel-2: #212c42;
  --fg: #e8edf7;
  --muted: #93a1bd;
  --accent: #5b8cff;
  --accent-2: #7c5bff;
  --good: #34d399;
  --bad: #f87171;
  --line: #2b3852;
  --chip: #243149;
  --radius: 14px;
  --shadow: 0 6px 20px rgba(0,0,0,.28);
}
@media (prefers-color-scheme: light) {
  :root {
    --bg: #f4f6fb; --panel: #ffffff; --panel-2: #eef2fa; --fg: #1a2233; --muted: #5c6b86;
    --line: #e0e6f1; --chip: #eaf0fc; --shadow: 0 4px 16px rgba(30,50,90,.10);
  }
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Apple SD Gothic Neo", "Noto Sans KR", sans-serif;
  background: var(--bg); color: var(--fg);
  padding-bottom: calc(74px + env(safe-area-inset-bottom));
  line-height: 1.5;
}
.app-header {
  padding: 18px 18px 12px; position: sticky; top: 0; z-index: 5;
  background: linear-gradient(180deg, var(--bg) 70%, transparent);
}
.app-header h1 { margin: 0; font-size: 22px; letter-spacing: .3px; }
.app-header .sub { margin: 2px 0 0; color: var(--muted); font-size: 13px; }
.view { padding: 4px 16px 20px; max-width: 720px; margin: 0 auto; }

/* Tab bar */
.tabbar {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 10;
  display: grid; grid-template-columns: repeat(4, 1fr);
  background: var(--panel); border-top: 1px solid var(--line);
  padding-bottom: env(safe-area-inset-bottom);
}
.tab {
  border: 0; background: transparent; color: var(--muted);
  padding: 10px 4px 12px; font-size: 11px; display: flex; flex-direction: column;
  align-items: center; gap: 3px; cursor: pointer; font-family: inherit;
}
.tab .ico { font-size: 20px; filter: grayscale(.3); }
.tab.active { color: var(--accent); }
.tab.active .ico { filter: none; }

/* Cards & panels */
.card {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 14px; margin: 12px 0; box-shadow: var(--shadow);
}
.section-title { font-size: 13px; color: var(--muted); text-transform: uppercase; letter-spacing: .6px; margin: 18px 4px 6px; }
.row { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }

/* Chips */
.chips { display: flex; gap: 8px; flex-wrap: wrap; }
.chip {
  background: var(--chip); border: 1px solid var(--line); color: var(--fg);
  padding: 7px 12px; border-radius: 999px; font-size: 14px; cursor: pointer; font-family: inherit;
}
.chip.active { background: var(--accent); border-color: var(--accent); color: #fff; }
.chip .ko { color: var(--muted); font-size: 12px; margin-left: 5px; }
.chip.active .ko { color: #dbe6ff; }

/* Buttons */
.btn {
  background: var(--accent); color: #fff; border: 0; border-radius: 10px;
  padding: 11px 16px; font-size: 15px; font-weight: 600; cursor: pointer; font-family: inherit;
}
.btn.secondary { background: var(--panel-2); color: var(--fg); border: 1px solid var(--line); }
.btn.ghost { background: transparent; color: var(--accent); padding: 6px 10px; }
.btn:active { transform: translateY(1px); }
.icon-btn { background: var(--panel-2); border: 1px solid var(--line); color: var(--fg); border-radius: 9px; padding: 8px 11px; cursor: pointer; font-size: 15px; }

/* Inputs */
input[type=text], select, textarea {
  width: 100%; background: var(--panel-2); border: 1px solid var(--line); color: var(--fg);
  border-radius: 10px; padding: 11px 12px; font-size: 15px; font-family: inherit;
}
textarea { min-height: 64px; resize: vertical; }
select { appearance: none; }

/* Builder preview */
.preview {
  font-size: 20px; font-weight: 600; line-height: 1.4; padding: 6px 2px 12px; word-break: break-word;
}
.preview .ph { color: var(--muted); border-bottom: 2px dashed var(--muted); padding: 0 6px; }

/* Reference item */
.ref-item { border-bottom: 1px solid var(--line); padding: 12px 2px; }
.ref-item:last-child { border-bottom: 0; }
.ref-word { font-size: 17px; font-weight: 700; }
.ref-ko { color: var(--accent); font-size: 14px; margin-left: 8px; }
.ref-uses { color: var(--muted); font-size: 13px; margin: 4px 0 6px; }
.ex { margin: 3px 0; font-size: 14px; }
.ex .en b { color: var(--accent); font-weight: 700; }
.ex .ko { color: var(--muted); font-size: 13px; }

/* Quiz */
.flash {
  min-height: 180px; display: flex; flex-direction: column; align-items: center; justify-content: center;
  text-align: center; gap: 10px; cursor: pointer; user-select: none;
}
.flash .big { font-size: 26px; font-weight: 700; }
.flash .hint { color: var(--muted); font-size: 13px; }
.opt {
  display: block; width: 100%; text-align: left; margin: 8px 0; padding: 13px 14px;
  background: var(--panel-2); border: 1px solid var(--line); border-radius: 11px;
  color: var(--fg); font-size: 16px; cursor: pointer; font-family: inherit;
}
.opt.correct { background: rgba(52,211,153,.18); border-color: var(--good); }
.opt.wrong { background: rgba(248,113,113,.16); border-color: var(--bad); }
.score { color: var(--muted); font-size: 13px; }
.seg { display: flex; gap: 6px; background: var(--panel-2); padding: 4px; border-radius: 11px; }
.seg button { flex: 1; border: 0; background: transparent; color: var(--muted); padding: 8px; border-radius: 8px; font-size: 14px; cursor: pointer; font-family: inherit; }
.seg button.active { background: var(--accent); color: #fff; }

/* My sentences */
.mine-item { display: flex; align-items: center; gap: 8px; padding: 11px 2px; border-bottom: 1px solid var(--line); }
.mine-item:last-child { border-bottom: 0; }
.mine-item .txt { flex: 1; font-size: 15px; word-break: break-word; }
.empty { color: var(--muted); text-align: center; padding: 40px 10px; font-size: 14px; }
.toast {
  position: fixed; left: 50%; transform: translateX(-50%); bottom: 92px; z-index: 30;
  background: var(--fg); color: var(--bg); padding: 10px 16px; border-radius: 999px; font-size: 14px;
  opacity: 0; transition: opacity .2s; pointer-events: none; font-weight: 600;
}
.toast.show { opacity: .96; }

/* ===== v2: 모바일 최적화 + 연습/교재 ===== */
html, body { overflow-x: hidden; max-width: 100%; }
.view, .card, .tabbar { max-width: 100%; }
.app-header h1 { font-size: 20px; }

/* 5-tab bar, 라벨 잘림 방지 */
.tabbar { grid-template-columns: repeat(5, 1fr); }
.tab { padding: 9px 2px 11px; font-size: 10.5px; }
.tab span:last-child { white-space: nowrap; }
.tab .ico { font-size: 19px; }

/* 연습(practice) */
.prompt-label { color: var(--muted); font-size: 12.5px; margin-bottom: 8px; }
.prompt-ko { font-size: 22px; font-weight: 700; line-height: 1.4; margin-bottom: 14px; word-break: keep-all; }
.hint-box { background: var(--panel-2); border: 1px dashed var(--line); border-radius: 10px; padding: 10px 12px; margin: 10px 0 0; font-size: 14px; color: var(--fg); }
.hint-box b { color: var(--accent); }
.feedback { font-weight: 700; margin: 14px 0 6px; font-size: 15px; }
.feedback.ok { color: var(--good); }
.feedback.bad { color: var(--bad); }
.model { background: var(--panel-2); border: 1px solid var(--line); border-radius: 10px; padding: 12px; }
.model .en { font-size: 16px; line-height: 1.5; }
.model .en b { color: var(--accent); font-weight: 800; }
.model .ko { color: var(--muted); font-size: 13px; margin-top: 3px; display: block; }

/* 교재(materials) */
.mat-intro { color: var(--muted); font-size: 13px; margin: 6px 2px 12px; }
.mat { margin: 0 0 16px; }
.mat h3 { font-size: 14px; margin: 0 0 8px; color: var(--fg); }
.mat a { display: block; }
.mat img { width: 100%; height: auto; display: block; border-radius: 12px; border: 1px solid var(--line); background: #fff; }
.mat .cap { color: var(--muted); font-size: 12px; margin-top: 6px; text-align: center; }

/* ===== v3: 순서 맞추기(단어 배치) ===== */
.build-answer {
  min-height: 54px; background: var(--panel-2); border: 1px dashed var(--accent);
  border-radius: 10px; padding: 10px; display: flex; flex-wrap: wrap; gap: 8px; margin: 8px 0 4px;
}
.build-answer:empty::before { content: "여기에 단어를 순서대로 놓으세요"; color: var(--muted); font-size: 13px; align-self: center; }
.build-source { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 6px; }
.wchip {
  background: var(--chip); border: 1px solid var(--line); color: var(--fg);
  padding: 9px 14px; border-radius: 10px; font-size: 16px; cursor: pointer; font-family: inherit;
}
.wchip:active { transform: translateY(1px); }
.build-answer .wchip { background: var(--accent); border-color: var(--accent); color: #fff; }