:root {
  --bg: #f4f6fb;
  --card: #ffffff;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #e5e7eb;
  --ok: #16a34a;
  --warn: #d97706;
  --danger: #dc2626;
  --radius: 14px;
  --shadow: 0 4px 20px rgba(0,0,0,0.06);
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans", "Microsoft YaHei", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.5;
}
#app { max-width: 1100px; margin: 0 auto; padding: 16px; }
h1, h2, h3 { margin: 0 0 12px; }
button { font: inherit; cursor: pointer; }
input, textarea, select { font: inherit; }

.center-screen { min-height: 92vh; display: flex; align-items: center; justify-content: center; }
.card {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 24px; width: 100%;
}
.card.narrow { max-width: 480px; }
.brand { text-align: center; margin-bottom: 8px; }
.brand h1 { font-size: 22px; color: var(--primary-dark); }
.brand p { color: var(--muted); margin: 0; font-size: 14px; }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  background: var(--primary); color: #fff; border: none; border-radius: 10px;
  padding: 12px 18px; font-weight: 600; transition: background .15s;
}
.btn:hover { background: var(--primary-dark); }
.btn:disabled { background: #9ca3af; cursor: not-allowed; }
.btn.block { width: 100%; }
.btn.ghost { background: transparent; color: var(--primary); border: 1px solid var(--border); }
.btn.ghost:hover { background: #f3f4f6; }
.btn.success { background: var(--ok); }
.btn.small { padding: 8px 12px; font-size: 14px; }

label { display: block; font-weight: 600; margin: 14px 0 6px; font-size: 14px; }
.hint { color: var(--muted); font-size: 13px; margin-top: 4px; }
input[type=text], input[type=number], textarea, select {
  width: 100%; padding: 12px; border: 1px solid var(--border); border-radius: 10px;
  background: #fff; color: var(--text);
}
textarea { resize: vertical; min-height: 120px; line-height: 1.6; }
.row { display: flex; gap: 10px; flex-wrap: wrap; }
.row > * { flex: 1; }

.lang-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 18px 0; }
.lang-btn {
  background: #fff; border: 2px solid var(--border); border-radius: 12px;
  padding: 18px 8px; font-weight: 600; color: var(--text); text-align: center;
}
.lang-btn.active { border-color: var(--primary); background: #eff6ff; color: var(--primary-dark); }

.tabs { display: flex; gap: 8px; margin-bottom: 14px; }
.tab { flex: 1; padding: 10px; text-align: center; border-radius: 10px; background: #f3f4f6;
  font-weight: 600; color: var(--muted); border: none; }
.tab.active { background: var(--primary); color: #fff; }

.consent-box { background: #f9fafb; border: 1px solid var(--border); border-radius: 10px;
  padding: 12px 14px; margin-top: 12px; }
.consent-item { display: flex; gap: 10px; align-items: flex-start; margin: 8px 0; font-size: 14px; }
.consent-item input { width: 18px; height: 18px; margin-top: 2px; flex: none; }
.consent-item label { margin: 0; font-weight: 400; }

.error { color: var(--danger); font-size: 14px; margin-top: 10px; }

.code-display { background: #eff6ff; border: 2px dashed var(--primary); border-radius: 12px;
  padding: 18px; text-align: center; margin: 16px 0; }
.code-display .code { font-size: 30px; font-weight: 800; letter-spacing: 4px; color: var(--primary-dark); }
.code-warn { color: var(--warn); font-size: 13px; margin-top: 10px; }

/* top bar */
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 10px;
  margin-bottom: 16px; flex-wrap: wrap; }
.topbar .who { font-size: 14px; color: var(--muted); }
.topbar .who b { color: var(--text); }
.topbar-actions { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.chip { background: #eef2ff; color: var(--primary-dark); padding: 4px 10px; border-radius: 999px;
  font-size: 12px; font-weight: 600; }
select.mini { width: auto; padding: 8px 10px; }

/* task cards */
.task-grid { display: grid; grid-template-columns: 1fr; gap: 14px; }
@media (min-width: 720px) { .task-grid { grid-template-columns: repeat(3, 1fr); } }
.task-card { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 18px; display: flex; flex-direction: column; }
.task-card h3 { color: var(--primary-dark); }
.task-card p { color: var(--muted); font-size: 14px; flex: 1; }
.task-card.disabled { opacity: .55; }
.progress-bar { height: 8px; background: #eef2f7; border-radius: 999px; overflow: hidden; margin: 10px 0; }
.progress-bar > span { display: block; height: 100%; background: var(--primary); }
.progress-text { font-size: 13px; color: var(--muted); margin-bottom: 10px; }

/* answering layout */
.answer-layout { display: flex; flex-direction: column; gap: 16px; }

.img-panel { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 12px; }
.img-stage { position: relative; width: 100%; overflow: hidden;
  background: #0b1220; border-radius: 10px; touch-action: none; line-height: 0; }
.img-stage img { display: block; width: 100%; height: auto; transform-origin: 0 0; user-select: none;
  -webkit-user-drag: none; will-change: transform; }
.img-tabs { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 8px; }
.img-tab { padding: 6px 10px; border-radius: 8px; background: #f3f4f6; border: 1px solid var(--border);
  font-size: 13px; color: var(--muted); }
.img-tab.active { background: var(--primary); color: #fff; border-color: var(--primary); }
.img-toolbar { display: flex; gap: 8px; align-items: center; margin-top: 8px; flex-wrap: wrap; }
.img-hint { color: var(--muted); font-size: 12px; flex: 1; }

.answer-panel { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 18px; }
.qprompt { background: #f9fafb; border: 1px solid var(--border); border-radius: 10px;
  padding: 12px; font-size: 14px; margin-bottom: 12px; }
.qhead { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin-bottom: 8px; }
.qhead .num { font-weight: 700; }
.badge { background: var(--ok); color: #fff; font-size: 12px; padding: 3px 8px; border-radius: 999px; }
.badge.gray { background: #9ca3af; }

/* score selector grids (confidence / difficulty) — same look as the question navigator */
.score-grid { display: flex; flex-wrap: wrap; gap: 10px; padding: 8px;
  border: 2px solid transparent; border-radius: 10px; transition: border-color .15s; }
.score-cell { width: 42px; height: 38px; border-radius: 8px; border: 1px solid var(--border);
  background: #fff; font-weight: 600; color: var(--text); font-size: 15px; }
.score-cell:hover { border-color: var(--primary); color: var(--primary-dark); }
.score-cell.selected { background: var(--ok); color: #fff; border-color: var(--ok); }
.score-grid.invalid { border-color: var(--danger); animation: shake .4s; }
.score-hint { color: var(--danger); font-size: 13px; margin: 4px 0 0 6px; display: none; }
.score-hint.show { display: block; }
@keyframes shake {
  0%,100% { transform: translateX(0); }
  20% { transform: translateX(-7px); }
  40% { transform: translateX(7px); }
  60% { transform: translateX(-5px); }
  80% { transform: translateX(5px); }
}

.slider-row { display: flex; align-items: center; gap: 10px; }
.slider-row input[type=range] { flex: 1; }
.slider-val { width: 34px; text-align: center; font-weight: 700; color: var(--primary-dark); }
.inline { display: flex; align-items: center; gap: 8px; }
.inline input[type=checkbox] { width: 18px; height: 18px; }

.nav-buttons { display: flex; gap: 8px; margin-top: 16px; flex-wrap: wrap; }
.nav-buttons .btn { flex: 1; }

.save-status { font-size: 12px; color: var(--muted); min-height: 16px; margin-top: 6px; }

/* question navigator */
.qnav-card { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 16px 18px; margin-top: 16px; }
.qnav-card h3 { font-size: 15px; margin-bottom: 10px; }
.qnav { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 14px; }
.qnav-card .qnav { margin-top: 0; }
.qnav-dot { width: 34px; height: 30px; border-radius: 8px; border: 1px solid var(--border);
  background: #fff; font-size: 12px; color: var(--muted); }
.qnav-dot.done { background: var(--ok); color: #fff; border-color: var(--ok); }
.qnav-dot.current { outline: 2px solid var(--primary); }

.modal-backdrop { position: fixed; inset: 0; background: rgba(0,0,0,.45); display: flex;
  align-items: center; justify-content: center; padding: 16px; z-index: 50; }
.modal { background: #fff; border-radius: var(--radius); padding: 22px; max-width: 480px; width: 100%;
  max-height: 90vh; overflow: auto; }

.radio-row { display: flex; gap: 8px; flex-wrap: wrap; margin: 6px 0; }
.radio-pill { padding: 8px 14px; border: 1px solid var(--border); border-radius: 999px; background: #fff; }
.radio-pill.active { background: var(--primary); color: #fff; border-color: var(--primary); }

.toast { position: fixed; bottom: 20px; left: 50%; transform: translateX(-50%) translateY(20px);
  background: #111827; color: #fff; padding: 10px 18px; border-radius: 10px; opacity: 0;
  transition: all .25s; pointer-events: none; z-index: 100; font-size: 14px; }
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

.spacer { height: 8px; }
.muted { color: var(--muted); font-size: 13px; }
.center { text-align: center; }