:root {
  --bg: #f3f4f8;
  --panel: #fff;
  --line: #dfe2ea;
  --text: #1c1f26;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-dark: #1d4ed8;
  --danger: #b91c1c;
  --radius: 10px;
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body { font-family: 'Segoe UI', system-ui, Arial, sans-serif; background: var(--bg); color: var(--text); font-size: 15px; line-height: 1.4; }
h1, h2, h3, h4 { margin: 0; font-weight: 700; }
h1 { font-size: 22px; }
h2 { font-size: 18px; margin-bottom: 12px; }
h3 { font-size: 16px; }
h4 { font-size: 14px; }
.muted { color: var(--muted); font-weight: 400; font-size: 13px; }
.muted.small { font-size: 12px; margin: 0; }
.placeholder { color: var(--muted); padding: 24px; text-align: center; border: 1px dashed var(--line); border-radius: var(--radius); background: var(--panel); }
.error { color: var(--danger); margin: 8px 0 0; }

.topbar { display: flex; align-items: baseline; gap: 14px; padding: 14px 24px; background: var(--panel); border-bottom: 1px solid var(--line); }
.topbar .sub { color: var(--muted); font-size: 13px; }

.layout { display: grid; grid-template-columns: 400px minmax(0, 1fr); gap: 20px; padding: 20px 24px; align-items: start; }
@media (max-width: 980px) { .layout { grid-template-columns: 1fr; } }

/* Конструктор */
.builder { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; }
.block { border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 12px; margin-bottom: 12px; }
.block-head { display: flex; align-items: center; gap: 8px; cursor: pointer; font-size: 15px; }
.block-head em { color: var(--muted); font-size: 12px; font-style: normal; }
.block .fields { margin-top: 8px; display: grid; gap: 6px; }
.block.disabled .fields { opacity: .45; pointer-events: none; }
.fields label { display: grid; grid-template-columns: 1fr 1.5fr; align-items: center; gap: 8px; font-size: 13px; }
.fields label > span:first-child { color: var(--muted); }
.fields select, .fields input[type=number] { width: 100%; padding: 5px 6px; border: 1px solid var(--line); border-radius: 6px; font: inherit; font-size: 13px; background: #fff; }
.fields .pair { display: flex; align-items: center; gap: 6px; }
.fields .pair select { width: auto; }
.fields .help { grid-column: 1 / -1; color: var(--muted); font-size: 12px; margin: -2px 0 2px; }

button, .btn { font: inherit; }
.primary { width: 100%; padding: 11px; border: 0; border-radius: var(--radius); background: var(--accent); color: #fff; font-weight: 700; font-size: 15px; cursor: pointer; }
.primary:hover { background: var(--accent-dark); }
.primary:disabled { opacity: .6; cursor: default; }

.btn { display: inline-block; padding: 8px 12px; border: 1px solid var(--line); border-radius: 8px; background: #fff; color: var(--text); text-decoration: none; cursor: pointer; font-size: 14px; line-height: 1.2; }
.btn:hover { border-color: #b9c0cf; background: #f8f9fc; }
.btn.small { padding: 5px 9px; font-size: 13px; }
.btn.accent { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.accent:hover { background: var(--accent-dark); }
.btn.danger { color: var(--danger); }
.actions { display: flex; flex-wrap: wrap; gap: 6px; }
.actions.big .btn { padding: 10px 14px; }

/* Комплект */
.assignment-head { display: flex; justify-content: space-between; align-items: flex-start; gap: 16px; flex-wrap: wrap; background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; margin-bottom: 16px; }
/* Группы типов заданий встают в колонки, пока хватает ширины; внутри группы карточки растут до 720px */
.groups { display: grid; grid-template-columns: repeat(auto-fit, minmax(440px, 1fr)); gap: 20px; align-items: start; }
.group { min-width: 0; }
.group-head { display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 10px; }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(380px, 720px)); gap: 14px; }
@media (max-width: 520px) { .groups, .cards { grid-template-columns: 1fr; } }
.sheet-card { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 12px; display: grid; gap: 10px; }
.sheet-card-head { display: flex; flex-direction: column; align-items: flex-start; gap: 8px; }
.toggle { display: flex; flex-wrap: wrap; gap: 4px; }
.chip { padding: 4px 10px; border: 1px solid var(--line); border-radius: 999px; background: #fff; font-size: 12px; cursor: pointer; color: var(--text); text-decoration: none; }
.chip.active { background: var(--text); color: #fff; border-color: var(--text); }
.chip.link { color: var(--accent); }
.preview-wrap { position: relative; width: 100%; aspect-ratio: 210 / 297; overflow: hidden; border: 1px solid var(--line); border-radius: 6px; background: #fff; }
.preview { position: absolute; top: 0; left: 0; width: 794px; height: 1123px; border: 0; transform-origin: 0 0; pointer-events: none; }

/* История */
.history { margin-top: 28px; }
.history-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 8px; }
.history-item { display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 14px; }
.history-item.current { border-color: var(--accent); box-shadow: 0 0 0 2px rgba(37, 99, 235, .15); }
.history-main { display: grid; gap: 2px; }