/* Week 1: diagrams and compact derivations form the main teaching route. */
.w1-lesson{margin:2rem 0 3rem;padding-bottom:2rem;border-bottom:1px solid var(--border)}
.w1-flow{display:flex;align-items:center;gap:16px;margin:24px 0}.w1-flow>div{flex:1;background:var(--surface);border:1px solid var(--border);border-radius:12px;padding:18px}.w1-flow strong{display:block;font-size:1.1rem}.w1-flow>.eyebrow{display:block}
.w1-figure{margin:24px 0;padding:22px;background:var(--surface);border:1px solid var(--border);border-radius:14px}.w1-figure figcaption{font-weight:600;margin-bottom:18px;color:var(--heading)}
.w1-cards{display:flex;gap:8px}.w1-card{flex:1;min-width:0;text-align:center;border:1px solid var(--border-strong);border-radius:8px;padding:12px 2px;font:600 1.25rem var(--font-mono);background:var(--bg-soft);color:var(--heading)}.w1-card.picked{border:2px solid var(--accent);background:var(--accent-soft)}.w1-card.faded{opacity:.3}
.w1-memory{display:flex;gap:8px;margin-top:8px}.w1-memory>span{flex:1;text-align:center;color:var(--green);font:600 1.25rem var(--font-mono)}.w1-memory>span:before{content:'↓';display:block;color:var(--muted);font-size:1rem;margin-bottom:8px}
.w1-caption{font-size:.9rem!important;margin-bottom:0!important}.w1-search-row{margin-bottom:20px}.w1-search-row>b{display:block;color:var(--accent);font-family:var(--font-mono);margin-bottom:6px}.w1-search-row p{font-size:.9rem;margin:6px 0 0}.w1-search-row:last-child{margin-bottom:0}
.w1-equations,.w1-compare{display:grid;grid-template-columns:repeat(auto-fit,minmax(190px,1fr));gap:14px;margin:22px 0}.w1-equations>div,.w1-compare>div{padding:18px;border:1px solid var(--border);border-radius:10px;background:var(--bg-soft)}.w1-equations span{display:block;font-size:.82rem;color:var(--muted);margin-bottom:10px}.w1-equations strong{display:block;font-family:Georgia,serif;font-size:1.65rem;font-weight:400;color:var(--heading)}.w1-compare h3{margin:0 0 8px}.w1-compare p{margin:0 0 8px;font-size:.95rem}
.w1-key{font-family:Georgia,serif;font-size:1.2rem;padding:16px;border-left:3px solid var(--accent);background:var(--accent-soft)}.w1-key strong{font-family:var(--font-body);font-size:.95rem}.w1-reference{font-size:.9rem;color:var(--muted)}
@media(max-width:540px){.w1-flow{gap:8px;flex-direction:column;align-items:stretch}.w1-flow>span{transform:rotate(90deg);align-self:center}.w1-flow>div{padding:12px}.w1-figure{padding:12px;margin:18px 0}.w1-cards{gap:4px}.w1-card{font-size:.88rem;padding:10px 0}.w1-equations,.w1-compare{grid-template-columns:1fr}.w1-key{font-size:1.05rem}.w1-lesson{margin:1.5rem 0;padding-bottom:1.5rem}}