.sample-day { margin: 0; background: var(--bg-page, #f5f6f8); color: var(--text-primary, #172d42); font: 1rem/1.65 system-ui, sans-serif; }
.sample-day * { box-sizing: border-box; }
.sample-day a { color: var(--blue, #245b99); }
.sample-day main { max-width: 1160px; margin: auto; padding: 0 28px; }
.sample-topbar { display: flex; align-items: center; justify-content: space-between; padding: 18px max(24px, calc((100vw - 1104px) / 2)); gap: 20px; background: var(--bg-panel, #fff); border-bottom: 1px solid var(--border, #dde4e9); }
.sample-brand { font-size: 1.2rem; font-weight: 800; text-decoration: none; white-space: nowrap; }
.sample-topbar nav { display: flex; gap: 22px; flex-wrap: wrap; font-size: .9rem; }
.sample-topbar nav a { text-decoration: none; }
.sample-hero { display: grid; grid-template-columns: 1fr 1.15fr; align-items: center; gap: 38px; padding: 64px 0 44px; }
.sample-kicker { font-size: .76rem; font-weight: 700; text-transform: uppercase; letter-spacing: .12em; color: var(--text-secondary, #52647b); }
.sample-day h1 { font: 600 clamp(2.3rem, 4vw, 3.4rem)/1.08 Georgia, serif; letter-spacing: -.035em; margin: 18px 0 24px; }
.sample-intro { font-size: 1.13rem; color: var(--text-secondary, #52647b); }
.sample-course { font-size: .92rem; margin: 24px 0; }
.sample-hero figure { margin: 0; border-radius: 16px; overflow: hidden; background: #102638; box-shadow: 0 18px 45px #0c274422; }
.sample-hero img { display: block; width: 100%; height: auto; }
.sample-hero figcaption { color: #d3e5f2; padding: 12px 18px; font-size: .78rem; }
.sample-sequence { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 12px; border-top: 1px solid var(--border, #dde4e9); border-bottom: 1px solid var(--border, #dde4e9); padding: 18px 0; }
.sample-sequence a { text-decoration: none; font-weight: 600; font-size: .93rem; }
.sample-sequence span { font-size: .75rem; color: var(--text-secondary, #52647b); margin-right: 8px; }
.sample-section { padding: 52px 0; border-bottom: 1px solid var(--border, #dde4e9); scroll-margin-top: 20px; }
.sample-section > p { max-width: 800px; }
.sample-section h2 { font: 600 clamp(1.7rem, 3vw, 2.35rem)/1.2 Georgia, serif; margin: 12px 0 20px; }
.sample-section h3 { font-size: 1.1rem; line-height: 1.4; margin: 12px 0; }
.sample-paper { display: grid; grid-template-columns: 1.3fr 1fr; gap: 60px; align-items: center; }
.sample-day .sample-button { display: inline-block; padding: 12px 18px; border: 1px solid #245b99; border-radius: 7px; background: #245b99; color: white; text-decoration: none; font: 600 .93rem/1.5 system-ui, sans-serif; cursor: pointer; }
.sample-day .sample-button[hidden] { display: none; }
.sample-day .sample-button:hover { background: #1c4879; }
.sample-small { font-size: .86rem; color: var(--text-secondary, #52647b); }
.sample-notebook { border: 1px solid var(--border, #dce2e9); border-radius: 12px; padding: 26px; background: var(--bg-panel, #fff); }
.sample-notebook > span { font-size: .8rem; text-transform: uppercase; letter-spacing: .1em; }
.sample-notebook strong { display: block; font-family: Georgia, serif; font-size: 1.22rem; }
.sample-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 18px; margin: 22px 0; }
.sample-secondary { font-size: .9rem; }
#sample-guide-host iframe { display: block; width: 100%; height: 880px; border: 1px solid var(--border, #cbd5e1); border-radius: 12px; background: white; }
.sample-problems { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-top: 28px; align-items: start; }
.sample-problem { border: 1px solid var(--border, #dce2e9); background: var(--bg-panel, #fff); border-radius: 12px; padding: 24px; }
.sample-problem p { margin: 10px 0; }
.sample-level { display: inline-block; font-size: .76rem; font-weight: 800; padding: 2px 9px; border-radius: 4px; }
.sample-level.easy { color: #176347; background: #e0f1e9; }.sample-level.medium { color: #275d9b; background: #e6eefb; }.sample-level.hard { color: #915414; background: #fff0d9; }.sample-level.boss { color: #704695; background: #f0e7f8; }
.sample-problem details { margin-top: 18px; border-top: 1px solid var(--border, #dce2e9); padding-top: 12px; }
.sample-problem summary { cursor: pointer; font-size: .9rem; font-weight: 600; }
.sample-equation { padding: 12px; border-radius: 6px; background: var(--bg-panel-alt, #f1f5f9); font-size: .95rem; line-height: 1.9; overflow-wrap: anywhere; }
.sample-next { margin-top: 28px; padding: 26px; border-left: 3px solid #245b99; background: var(--bg-panel, #fff); }
.sample-closing { text-align: center; }.sample-closing > p { margin: 18px auto; }
.sample-footer { padding: 30px 24px; text-align: center; font-size: .82rem; color: var(--text-secondary, #52647b); }
.sample-day :focus-visible { outline: 3px solid #4f8ad9; outline-offset: 4px; }
.sample-skip { position: absolute; left: 10px; top: -100px; padding: 10px; background: white; z-index: 5; }.sample-skip:focus { top: 10px; }
@media (max-width: 760px) { .sample-hero, .sample-paper, .sample-problems { grid-template-columns: 1fr; gap: 24px; }.sample-hero { padding-top: 32px; }.sample-section { padding: 36px 0; }.sample-topbar { align-items: flex-start; }.sample-topbar nav { gap: 8px 14px; justify-content: flex-end; }.sample-day main { padding: 0 20px; }.sample-problem { padding: 20px; } }
@media (prefers-reduced-motion: reduce) { .sample-day * { scroll-behavior: auto !important; } }