:root { color-scheme: light; --paper: #f4f1e9; --ink: #111110; --muted: #59574f; --line: #c7c2b8; --green: #244f43; }
* { box-sizing: border-box; }
html { background: var(--paper); scroll-padding-top: 24px; }
body { margin: 0; color: var(--ink); background: var(--paper); font-family: Helvetica, "Helvetica Neue", Arial, "Hiragino Sans", "Yu Gothic", sans-serif; font-size: 16px; line-height: 1.85; -webkit-font-smoothing: antialiased; }
a { color: inherit; text-underline-offset: 5px; }
a:hover { color: var(--green); }
:focus-visible { outline: 3px solid var(--green); outline-offset: 5px; }
.skip { position: absolute; left: 16px; top: -100px; padding: 8px; background: var(--paper); }
.skip:focus { top: 8px; }
.header { max-width: 1120px; margin: auto; padding: 24px; display: flex; align-items: center; justify-content: space-between; gap: 18px; border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; flex: none; width: 148px; max-width: 45%; min-height: 44px; text-decoration: none; }
.brand img { display: block; width: 100%; height: auto; }
.header nav { font-size: 14px; }
main { max-width: 768px; margin: auto; padding: 42px 24px 72px; }
.breadcrumb { display: flex; flex-wrap: wrap; gap: 8px; color: var(--muted); font-size: 13px; margin-bottom: 36px; }
.eyebrow { color: var(--green); font-size: 14px; letter-spacing: .03em; font-weight: 600; }
.guide-category { display: flex; align-items: center; flex-wrap: wrap; gap: 8px 12px; margin: 0 0 12px; color: var(--green); font-size: 16px; font-weight: 600; line-height: 1.5; }
.topic-tag { padding: 2px 8px; background: #e3e9df; font-size: 14px; font-weight: 500; }
h1 { font-size: clamp(26px, 3vw, 32px); line-height: 1.5; letter-spacing: -.02em; margin: 0 0 24px; font-weight: 600; text-wrap: pretty; }
h2 { margin: 40px 0 16px; font-size: clamp(22px, 2.5vw, 26px); line-height: 1.6; font-weight: 600; }
h3 { font-size: 20px; line-height: 1.6; }
p { margin: 16px 0; }
.meta, .note { font-size: 14px; color: var(--muted); }
.lead { font-size: 16px; }
.problem { margin: 32px 0; padding: 24px; border: 1px solid var(--ink); }
.problem p { margin: 8px 0 0; }
.label { font-size: 13px; font-weight: 700; color: var(--green); }
.fraction { font-variant-numeric: tabular-nums; white-space: nowrap; }
figure { margin: 32px 0; }
.bar { display: flex; height: 54px; border: 1px solid var(--ink); }
.bar span { display: flex; align-items: center; justify-content: center; font-size: 15px; font-weight: 700; }
.bar .thirty { width: 30%; background: var(--green); color: white; }
.bar .five { width: 5%; background: #c8d8ce; border-right: 1px solid var(--ink); }
.bar .rest { width: 65%; color: var(--muted); }
figcaption { margin-top: 12px; font-size: 14px; line-height: 1.8; }
.legend { display: flex; flex-wrap: wrap; gap: 8px 24px; font-size: 14px; margin-top: 12px; }
.swatch { display: inline-block; width: 12px; height: 12px; margin-right: 6px; background: var(--green); }
.swatch.light { background: #c8d8ce; border: 1px solid #77867c; }
.steps { padding: 0; list-style: none; counter-reset: step; }
.steps > li { counter-increment: step; border-top: 1px solid var(--line); padding: 24px 0; }
.steps h3 { margin: 0 0 12px; }
.steps h3::before { content: counter(step, decimal-leading-zero) " / "; color: var(--green); font-size: 15px; }
.steps p { margin: 10px 0; }
.equation { font-size: clamp(21px, 4.5vw, 28px); font-variant-numeric: tabular-nums; font-weight: 500; }
.answer { background: #e3e9df; padding: 20px 24px; border-left: 3px solid var(--green); }
.answer p { margin: 4px 0; }
details { border-block: 1px solid var(--line); padding: 16px 0; margin: 20px 0; }
summary { cursor: pointer; padding: 8px 0; font-weight: 700; }
.cta { margin-top: 48px; padding: 28px; border: 1px solid var(--green); }
.cta h2 { margin-top: 0; }
.button { display: inline-block; background: var(--green); color: white; padding: 12px 18px; text-decoration: none; font-size: 16px; }
.button:hover { color: white; background: #173b30; }
.article-card { border-block: 1px solid var(--line); margin: 32px 0; padding: 24px 0; }
.article-card h2 { margin: 0 0 14px; font-size: clamp(20px, 2.2vw, 24px); line-height: 1.6; letter-spacing: -.015em; text-wrap: pretty; }
footer { border-top: 1px solid var(--line); padding: 24px; max-width: 1120px; margin: auto; font-size: 13px; color: var(--muted); display: flex; flex-wrap: wrap; justify-content: space-between; gap: 16px; }
@media (max-width: 380px) { main { padding-inline: 20px; } .problem, .cta { padding: 20px; } .header { padding: 20px; } }