:root {
  color-scheme: light;
  --ink: #122541;
  --muted: #62728a;
  --line: #dce5ef;
  --surface: #ffffff;
  --background: #f3f6fa;
  --blue: #1769aa;
  --blue-dark: #10578f;
  --green: #16794c;
  --red: #b42318;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--background);
  color: var(--ink);
}

button, input, select, textarea { font: inherit; }
button { cursor: pointer; }
.hidden { display: none !important; }
.muted { color: var(--muted); }

.shell { max-width: 1180px; min-height: 100vh; margin: 0 auto; padding: 0 28px; }
.topbar { height: 76px; display: flex; align-items: center; justify-content: space-between; border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); font-size: 19px; font-weight: 750; text-decoration: none; }
.brand-mark { display: grid; width: 34px; height: 34px; place-items: center; border-radius: 11px; background: var(--blue); color: white; }
.account { display: flex; align-items: center; gap: 14px; font-size: 14px; }

.auth-layout { min-height: calc(100vh - 135px); display: grid; grid-template-columns: 1.15fr 0.85fr; align-items: center; gap: 50px; }
.intro { max-width: 570px; }
.intro h1 { margin: 12px 0 16px; font-size: clamp(36px, 5vw, 58px); letter-spacing: -0.045em; line-height: 1.05; }
.intro p:not(.eyebrow) { max-width: 480px; color: var(--muted); font-size: 18px; line-height: 1.65; }
.eyebrow { margin: 0 0 8px; color: var(--blue); font-size: 12px; font-weight: 750; letter-spacing: .12em; text-transform: uppercase; }

.card { margin-bottom: 22px; padding: 24px; border: 1px solid var(--line); border-radius: 16px; background: var(--surface); box-shadow: 0 7px 24px rgba(18, 37, 65, .04); }
.auth-card { padding: 20px; }
.tabs { display: flex; gap: 8px; border-bottom: 1px solid var(--line); }
.tab { padding: 12px 14px; border: 0; border-bottom: 2px solid transparent; background: transparent; color: var(--muted); font-weight: 650; }
.tab.active { border-bottom-color: var(--blue); color: var(--blue); }
.auth-form, .form-grid { display: grid; gap: 16px; }
.auth-form { padding-top: 20px; }
label { display: grid; gap: 7px; color: var(--ink); font-size: 13px; font-weight: 650; }
input, select, textarea { width: 100%; padding: 11px 12px; border: 1px solid #cbd6e2; border-radius: 8px; background: white; color: var(--ink); }
textarea { resize: vertical; font-family: "Cascadia Code", Consolas, monospace; font-size: 12px; line-height: 1.5; }
input:focus, select:focus, textarea:focus { outline: 3px solid rgba(23, 105, 170, .16); border-color: var(--blue); }
.button { min-height: 40px; padding: 9px 15px; border: 1px solid transparent; border-radius: 8px; font-weight: 700; }
.button-primary { background: var(--blue); color: white; }
.button-primary:hover { background: var(--blue-dark); }
.button-quiet { border-color: var(--line); background: white; color: var(--ink); }
.button-danger { border-color: #f2c8c5; background: #fff6f5; color: var(--red); }
.button-success { border-color: #b4e1ca; background: #effaf4; color: var(--green); }
.message { min-height: 20px; margin: 12px 0 0; color: var(--muted); font-size: 14px; }
.message.error { color: var(--red); }
.message.success { color: var(--green); }

.app-tabs { margin: 28px 0; }
.section-heading { display: flex; align-items: center; justify-content: space-between; gap: 16px; margin: 28px 0 18px; }
h1, h2, h3, p { margin-top: 0; }
h1 { margin-bottom: 0; font-size: 32px; letter-spacing: -.03em; }
h2 { font-size: 18px; }
.exam-list { display: grid; grid-template-columns: repeat(auto-fit, minmax(270px, 1fr)); gap: 16px; }
.exam-card { display: grid; gap: 12px; padding: 20px; border: 1px solid var(--line); border-radius: 14px; background: var(--surface); }
.exam-card h2 { margin: 0; }
.exam-card p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.5; }
.exam-actions { display: flex; flex-wrap: wrap; gap: 8px; }
.registration-controls { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.paper-panel { min-height: 260px; }
.paper-header { display: flex; align-items: flex-start; justify-content: space-between; gap: 18px; }
.paper-header h2 { margin-bottom: 4px; }
.question-layout { display: grid; grid-template-columns: minmax(0, 1fr) 220px; gap: 22px; margin-top: 22px; }
.question-body { min-height: 280px; }
.question-body h3 { margin: 8px 0 20px; font-size: 21px; line-height: 1.5; }
.option-list { display: grid; gap: 10px; }
.option { display: flex; align-items: flex-start; gap: 10px; padding: 12px; border: 1px solid var(--line); border-radius: 9px; font-weight: 450; line-height: 1.4; }
.option input { width: auto; margin: 2px 0 0; }
.question-nav { display: grid; grid-template-columns: repeat(5, 1fr); align-content: start; gap: 7px; }
.question-nav button { aspect-ratio: 1; border: 1px solid var(--line); border-radius: 7px; background: white; color: var(--ink); }
.question-nav button.current { border-color: var(--blue); background: #eaf4fc; color: var(--blue); }
.question-nav button.answered { border-color: #8acbab; background: #edf9f2; }
.paper-controls { display: flex; justify-content: space-between; gap: 12px; margin-top: 18px; }
.paper-controls div { display: flex; gap: 8px; }
.form-grid { grid-template-columns: 1fr 1fr; align-items: start; }
.form-grid h2, .form-grid .full, .form-grid button { grid-column: 1 / -1; }
.checkbox { display: flex; align-items: center; gap: 9px; }
.checkbox input { width: auto; }
.admin-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.registration-row { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 14px 0; border-bottom: 1px solid var(--line); }
.registration-row:last-child { border-bottom: 0; }
.registration-row p { margin: 4px 0 0; color: var(--muted); font-size: 13px; }
.registration-row .actions { display: flex; gap: 7px; }
.paper-history-row { padding: 14px 0; border-bottom: 1px solid var(--line); }
.paper-history-row:last-child { border-bottom: 0; }
.paper-history-row summary { cursor: pointer; font-size: 14px; font-weight: 650; }
.attempt-answers { margin: 12px 0; padding-left: 18px; color: var(--muted); font-size: 13px; line-height: 1.5; }
.grading-submission { margin-top: 18px; padding-top: 18px; border-top: 1px solid var(--line); }
.grading-question { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 14px 0; padding: 14px; border: 1px solid var(--line); border-radius: 10px; }
.grading-question p { grid-column: 1 / -1; margin: 0; line-height: 1.5; }
.leaderboard-row { display: grid; grid-template-columns: 50px 1fr auto; gap: 12px; padding: 10px 0; border-bottom: 1px solid var(--line); }
.pattern-structure { display: grid; gap: 14px; }
.pattern-structure h3 { margin: 18px 0 4px; font-size: 16px; }
.pattern-subject, .pattern-group, .pattern-category { padding: 16px; border: 1px solid var(--line); border-radius: 10px; background: #fbfcfe; }
.pattern-subject h3, .pattern-group h4, .pattern-category h3 { margin: 0 0 12px; }
.pattern-group { margin-top: 14px; background: white; }
.pattern-topic { margin-top: 12px; padding: 12px; border: 1px solid var(--line); border-radius: 8px; background: white; }
.pattern-fields { display: grid; grid-template-columns: repeat(auto-fit, minmax(145px, 1fr)); gap: 10px; margin-top: 10px; }
.pattern-field { font-size: 12px; }
.pattern-field input { padding: 8px; }
.pattern-field.checkbox { display: flex; justify-content: space-between; }
.pattern-field.checkbox input { margin-left: 8px; }
footer { display: flex; justify-content: space-between; padding: 24px 0; color: var(--muted); font-size: 12px; }

@media (max-width: 760px) {
  .shell { padding: 0 16px; }
  .auth-layout { min-height: auto; grid-template-columns: 1fr; gap: 20px; padding: 42px 0; }
  .intro h1 { font-size: 42px; }
  .admin-grid, .form-grid, .question-layout { grid-template-columns: 1fr; }
  .grading-question { grid-template-columns: 1fr; }
  .question-nav { grid-template-columns: repeat(8, 1fr); order: -1; }
  .registration-row { align-items: flex-start; flex-direction: column; }
  footer { gap: 12px; }
}