/* Short, formula-first topics shared by the academy and study room. */
.formula-lesson { font-size: 1rem; line-height: 1.7; }
.formula-lesson .lesson-roadmap { margin: 0 0 22px; color: #48615c; }
.formula-lesson .visual-step[open] > summary { border-bottom: 1px solid #d3e4df; background: #f3f8f5; }
.formula-lesson summary:focus-visible,
.formula-lesson button:focus-visible,
.formula-lesson a:focus-visible { outline: 3px solid #875313; outline-offset: -3px; }
.formula-lesson .guided-topic { min-width: 0; overflow-wrap: anywhere; }
.formula-lesson .step-label { margin: 28px 0 10px; font-size: .95rem; line-height: 1.5; color: #166256; }
.formula-lesson .step-label:first-child { margin-top: 0; }
.formula-lesson .formula-box { border: 1px solid #add0c2; border-left: 5px solid #166256; border-radius: 12px; padding: 4px 20px; background: #edf7f1; }
.formula-lesson .formula-row { padding: 14px 0; }
.formula-lesson .formula-row + .formula-row { border-top: 1px dashed #bdd8ca; }
.formula-lesson .formula-text { margin: 0; font-size: clamp(1.12rem, 2vw, 1.45rem); font-weight: 750; line-height: 1.65; color: #123e37; }
.formula-lesson .formula-meaning { margin: 5px 0 0; color: #415e53; }
.formula-lesson .visual-split { grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr); gap: 24px; align-items: start; }
.formula-lesson .guided-example { background: #f6f3fa; border: 1px solid #e2d8ed; border-radius: 12px; padding: 18px; min-width: 0; }
.formula-lesson .guided-example > :first-child { margin-top: 0; }
.formula-lesson .guided-example .jp,
.formula-lesson .guided-answer .jp { font-size: clamp(1.15rem, 2vw, 1.4rem); line-height: 1.8; font-weight: 600; color: #543177; }
.formula-lesson .example-analysis { border-top: 1px solid #e2d8ed; padding-top: 12px; color: #514a60; }
.formula-lesson .guided-example button { min-height: 44px; font: inherit; cursor: pointer; }
.formula-lesson .guided-tip { padding: 12px 16px; background: #fff7e7; border-left: 3px solid #c59639; border-radius: 8px; color: #644d23; }
.formula-lesson .guided-question { font-size: 1.08rem; font-weight: 600; }
.formula-lesson .visual-check summary { font-size: 1rem; min-height: 44px; }
.formula-lesson .guided-answer { padding: 0 18px 14px; }
.formula-lesson .guided-answer p:last-child { margin-bottom: 0; }
.formula-lesson .lesson-scene { max-width: 300px; margin: auto; }
.formula-lesson figcaption { line-height: 1.5; }
.formula-lesson .visual-reference { margin-top: 26px; }
@media (max-width: 850px) {
  .formula-lesson .visual-split { grid-template-columns: minmax(0, 1fr); gap: 18px; }
  .formula-lesson .visual-split figure { width: 100%; max-width: 420px; margin: auto; }
  .formula-lesson .formula-box { padding: 2px 14px; }
  .formula-lesson .guided-example { padding: 14px; }
}