/* Scoped teaching demonstration. Shared site styles remain untouched. */
.spread-example{max-width:1080px;margin:32px auto 0;color:#30392e}
.spread-question{font-size:18px;line-height:1.9;margin:0 0 28px;max-width:800px}.spread-question strong{font-weight:600}
.spread-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:24px}
.spread-card{border-top:2px solid #87917d;padding:22px 0 0;min-width:0}.spread-card .spread-number{font-size:12px;font-weight:600;letter-spacing:.15em;color:#59684b;margin:0 0 12px}
.spread-card h3{font-size:18px;line-height:1.65;font-weight:600;margin:0;min-height:60px}.spread-card>p:last-child{font-size:15px;line-height:1.9;margin:14px 0 0}
.spread-plot{display:block;width:100%;height:auto;margin:16px 0 0;background:#f5f4ed;border-radius:3px;padding:12px 5px;box-sizing:border-box;overflow:visible}
.spread-axis{stroke:#a3aa98;stroke-width:1}.spread-axis text{fill:#59614f;stroke:none;text-anchor:middle;font-size:12px;font-family:inherit}
.spread-mean{stroke:#59684b;stroke-width:1.5;stroke-dasharray:3 3}.spread-mean-label{fill:#394737;text-anchor:middle;font-size:13px;font-family:inherit}.spread-dots{fill:#526642}.spread-unit{fill:#59614f;text-anchor:end;font-size:10px;font-family:inherit}
.spread-bridge{display:grid;grid-template-columns:1fr 1.2fr;gap:40px;border-top:1px solid #d8dbcf;margin-top:38px;padding-top:30px}.spread-bridge h3{font-size:23px;line-height:1.7;font-weight:500;margin:8px 0}.spread-bridge p{font-size:15px;line-height:1.9;margin-top:0}.spread-bridge .spread-formula{font-size:19px;line-height:1.9;letter-spacing:0;margin:18px 0 8px}.spread-bridge .spread-notation{font-size:13px;color:#565e50}
.spread-practice{margin-top:26px;border:1px solid #c5cbbb;border-radius:3px;background:#f5f4ed}.spread-practice>summary{padding:19px 22px;font-size:16px;font-weight:600;cursor:pointer;line-height:1.7}.spread-practice>div{padding:0 22px 20px}.spread-practice p{font-size:15px;line-height:1.9}.spread-answer{border-top:1px solid #c5cbbb;margin-top:20px;padding-top:16px}.spread-answer summary{cursor:pointer;font-size:15px;line-height:1.7;color:#394737;text-decoration:underline;text-underline-offset:4px}.spread-scope{max-width:880px;font-size:15px;line-height:1.9;margin:28px 0 12px}
@media(max-width:800px){.spread-grid{grid-template-columns:1fr;gap:28px}.spread-example{margin-top:24px}.spread-question{font-size:16px}.spread-card h3{min-height:0;font-size:19px}.spread-plot{max-width:480px}.spread-bridge{grid-template-columns:1fr;gap:12px;margin-top:30px;padding-top:24px}.spread-bridge h3{font-size:22px}.spread-bridge .spread-formula{font-size:18px}.spread-practice>summary{padding:16px;font-size:15px}.spread-practice>div{padding:0 16px 16px}}