:root {
  --bg: #f4f6fa; --card: #fff; --ink: #1d2433; --muted: #6b7486; --line: #e2e6ee;
  --brand: #2f5bea; --brand-soft: #eaf0ff; --warn: #c2410c; --warn-soft: #fff1e8; --ok: #15803d; --ok-soft: #e8f7ee;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.6 Pretendard, system-ui, sans-serif; word-break: keep-all; }
.app { max-width: 920px; margin: 0 auto; padding: 0 16px 40px; }
h1, h2 { margin: 0 0 8px; line-height: 1.3; }
h1 { font-size: 26px; } h2 { font-size: 21px; }
small { font-weight: 400; }
.muted { color: var(--muted); margin: 4px 0 12px; font-size: 15px; }
.top { display: flex; justify-content: space-between; align-items: center; gap: 12px; padding: 18px 0; flex-wrap: wrap; }
.brand { font-weight: 800; font-size: 19px; }
.brand small { font-size: 13px; color: var(--brand); background: var(--brand-soft); padding: 2px 8px; border-radius: 99px; margin-left: 4px; }
.me { font-size: 14px; color: var(--muted); }
.me b { color: var(--brand); font-size: 16px; }
.tabs { display: flex; gap: 6px; overflow-x: auto; margin-bottom: 14px; }
.tabs button { flex: 1 0 auto; border: 1px solid var(--line); background: #fff; border-radius: 10px; padding: 10px 12px; font-weight: 600; color: var(--muted); }
.tabs button.on { background: var(--brand); border-color: var(--brand); color: #fff; }
.tabs button:disabled { opacity: .45; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 16px; padding: 24px; margin-bottom: 16px; }
.narrow { max-width: 440px; margin: 40px auto; }
label { display: block; font-weight: 600; margin: 14px 0 0; font-size: 15px; }
input:not([type=checkbox]):not([type=file]), textarea, select {
  display: block; width: 100%; margin-top: 6px; padding: 11px 12px; border: 1px solid var(--line); border-radius: 10px; font: inherit; font-weight: 400; background: #fff; }
input:focus, textarea:focus, select:focus { outline: 2px solid var(--brand); border-color: transparent; }
label.check { display: flex; gap: 8px; align-items: center; font-weight: 500; }
label.check input { width: 18px; height: 18px; }
button { font: inherit; cursor: pointer; border: 1px solid var(--line); background: #fff; border-radius: 10px; padding: 11px 16px; font-weight: 600; }
button.primary { background: var(--brand); border-color: var(--brand); color: #fff; width: 100%; margin-top: 18px; padding: 14px; font-size: 17px; }
button.small { width: auto; margin: 0; padding: 9px 14px; font-size: 15px; }
button.link { border: 0; background: none; padding: 0 0 0 6px; color: var(--muted); text-decoration: underline; font-weight: 400; }
button:disabled { opacity: .5; cursor: default; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 14px; }
.row button.primary { width: auto; flex: 1; margin: 0; }
.row-between { display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; }
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 0 14px; }
.msg { min-height: 1.2em; color: var(--warn); font-weight: 600; margin: 10px 0 0; }
.msg.ok { color: var(--ok); }
.tip { margin-top: 14px; background: var(--brand-soft); border-radius: 10px; padding: 12px 14px; font-size: 14px; }
.req, .opt { font-size: 12px; font-weight: 600; padding: 1px 7px; border-radius: 99px; margin-left: 4px; vertical-align: 2px; }
.req { background: var(--warn-soft); color: var(--warn); } .opt { background: #eef0f4; color: var(--muted); }

.drop { border: 2px dashed var(--line); border-radius: 12px; padding: 14px 16px; margin-top: 12px; }
.drop.over { border-color: var(--brand); background: var(--brand-soft); }
.drop .muted { margin: 2px 0 8px; font-size: 14px; }
.files { list-style: none; margin: 8px 0 0; padding: 0; font-size: 14px; }
.files li { display: flex; justify-content: space-between; gap: 8px; padding: 4px 0; border-top: 1px solid var(--line); }
.files li button { padding: 0 8px; font-size: 13px; }

.history { list-style: none; padding: 0; margin: 0; }
.history li { display: flex; justify-content: space-between; align-items: center; gap: 10px; padding: 10px 0; border-top: 1px solid var(--line); }
.history li:first-child { border-top: 0; }
.history .when { color: var(--muted); font-size: 13px; }

.chips { display: flex; flex-wrap: wrap; gap: 6px; margin: 8px 0 16px; }
.chip { background: #eef0f4; border-radius: 99px; padding: 3px 10px; font-size: 13px; font-weight: 600; }
.chip.warn { background: var(--warn-soft); color: var(--warn); } .chip.ok { background: var(--ok-soft); color: var(--ok); }

.q { border: 1px solid var(--line); border-radius: 12px; padding: 16px; margin-top: 12px; }
.q.review { border-color: #f5b68a; background: #fffaf6; }
.q-head { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; margin-bottom: 8px; }
.q-no { font-weight: 800; font-size: 18px; }
.q dl { display: grid; grid-template-columns: 92px 1fr; gap: 4px 10px; margin: 0; font-size: 15px; }
.q dt { color: var(--muted); } .q dd { margin: 0; }
.q .answers { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 10px 0; }
.q .answers div { background: var(--bg); border-radius: 10px; padding: 8px 10px; font-size: 14px; }
.q .answers b { display: block; font-size: 17px; }
.q .answers input { margin-top: 2px; padding: 6px 8px; }
.q .why { color: var(--warn); font-size: 14px; font-weight: 600; margin: 0 0 8px; }
.q .why.note { color: var(--muted); }
.q .recheck { margin-top: 10px; font-size: 14px; padding: 8px 12px; }

.rep h3 { font-size: 17px; margin: 22px 0 6px; padding-left: 10px; border-left: 4px solid var(--brand); }
.rep ul { margin: 4px 0; padding-left: 20px; }
.rep p { margin: 4px 0; }
table { width: 100%; border-collapse: collapse; font-size: 14px; margin-top: 6px; }
th, td { border: 1px solid var(--line); padding: 7px 8px; text-align: left; vertical-align: top; }
th { background: var(--bg); font-weight: 700; white-space: nowrap; }
.bar { height: 8px; background: var(--brand); border-radius: 99px; min-width: 2px; }

.grade-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 8px; margin-top: 16px; }
.g { border: 1px solid var(--line); border-radius: 10px; padding: 8px 10px; font-size: 14px; }
.g.right { border-color: #9bd8b1; background: var(--ok-soft); } .g.wrong { border-color: #f5b68a; background: var(--warn-soft); }
.g b { display: block; } .g input, .g select { margin-top: 4px; padding: 6px 8px; }
.g small { color: var(--muted); }
.score { font-size: 20px; font-weight: 800; margin: 16px 0 0; }

.foot { text-align: center; color: var(--muted); font-size: 13px; margin-top: 24px; }
#busy { position: fixed; inset: 0; background: rgba(20, 26, 40, .55); display: grid; place-items: center; z-index: 9; padding: 16px; }
#busy[hidden] { display: none; }
.busy-box { background: #fff; border-radius: 16px; padding: 28px 32px; text-align: center; max-width: 360px; }
.busy-box p { font-weight: 700; margin: 14px 0 4px; }
.spin { width: 40px; height: 40px; margin: 0 auto; border: 4px solid var(--brand-soft); border-top-color: var(--brand); border-radius: 50%; animation: spin 1s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
@media (prefers-reduced-motion: reduce) { .spin { animation-duration: 3s; } }

@media (max-width: 600px) {
  .card { padding: 18px; } .grid2 { grid-template-columns: 1fr; }
  .q .answers { grid-template-columns: 1fr; } .q dl { grid-template-columns: 76px 1fr; }
}
/* PDF 미리보기: A4 한 장처럼 보이게 */
#preview { position: fixed; inset: 0; z-index: 8; background: #5b6272; display: flex; flex-direction: column; }
.pv-bar { display: flex; justify-content: space-between; align-items: center; gap: 10px; padding: 10px 16px; background: #fff; flex-wrap: wrap; }
.pv-btns { display: flex; gap: 8px; }
.pv-scroll { flex: 1; overflow: auto; padding: 20px 16px; }
.sheet { background: #fff; color: var(--ink); max-width: 794px; margin: 0 auto; padding: 48px 44px; box-shadow: 0 4px 20px rgba(0,0,0,.25); font-size: 13.5px; }
.sheet h1 { font-size: 23px; } .sheet .sub { color: var(--muted); margin: 0 0 12px; }
.sheet.pdf { width: 690px; margin: 0; max-width: none; padding: 0; box-shadow: none; }
@media (max-width: 600px) { .sheet { padding: 24px 18px; } }

/* 과목 선택 · 부분 점수 · 수학 풀이 줄바꿈 */
.seg { display: inline-flex; background: var(--bg); border-radius: 12px; padding: 4px; gap: 4px; margin-bottom: 14px; }
.seg button { border: 0; background: none; padding: 8px 22px; border-radius: 9px; color: var(--muted); }
.seg button.on { background: #fff; color: var(--brand); box-shadow: 0 1px 3px rgba(0,0,0,.12); }
.g.part { border-color: #f1d27a; background: #fff8e1; }
dd.pre { white-space: pre-line; }