/* Only demo styling; existing site CSS is unchanged. */
.nx-demo-heading{padding-bottom:1rem}.nx-demo-shell{max-width:850px;margin-inline:auto;background:#fff;border:1px solid #dbe9ef;border-radius:22px;box-shadow:0 14px 38px rgba(9,48,75,.07);padding:clamp(1.25rem,4vw,2.5rem)}
.nx-demo-top,.nx-demo-navigation{display:flex;align-items:center;justify-content:space-between;gap:1rem}.nx-demo-stage{color:#52798d;font-size:.875rem}.nx-demo-progress{height:9px;background:#e5f2f6;border-radius:100px;overflow:hidden;margin:1.15rem 0 2rem}.nx-demo-progress>div{height:100%;width:0;background:#0f9e9b;transition:width .2s ease}.nx-demo-navigation{margin-top:2rem;border-top:1px solid #e4edf1;padding-top:1.4rem}.nx-demo-navigation .btn{min-width:124px}.nx-lesson h2{margin-bottom:1rem}.nx-lesson p{line-height:1.75}.nx-lesson-note{background:#edf9f9;border-left:4px solid #0f9e9b;border-radius:10px;padding:1rem 1.2rem;margin-top:1.5rem}.nx-gases{display:grid;gap:1.1rem;margin:1.6rem 0}.nx-gas-row{display:grid;grid-template-columns:110px 1fr 75px;gap:.7rem;align-items:center}.nx-gas-track{display:flex;height:23px;border-radius:7px;overflow:hidden;background:#b4d8ee}.nx-gas-oxygen{background:#14a49b}.nx-gas-label{font-weight:600}.nx-gas-key{display:flex;flex-wrap:wrap;gap:1.3rem;font-size:.8rem;color:#436279}.nx-gas-key i{display:inline-block;width:12px;height:12px;margin-right:6px;border-radius:3px;vertical-align:-1px}.nx-quiz-question{border:1px solid #e2ebee;border-radius:15px;padding:1.2rem;margin-bottom:1rem}.nx-quiz-question legend{font-weight:700;font-size:1.04rem;margin-bottom:1rem}.nx-option{display:flex;align-items:flex-start;gap:.6rem;padding:.5rem;border-radius:8px;cursor:pointer}.nx-option:hover{background:#f0f9fa}.nx-result{padding:1.3rem;border-radius:14px;background:#ebf8f5;margin-top:1.2rem}.nx-back-link{text-decoration:none;color:#15556c}.nx-back-link:hover{text-decoration:underline}@media(max-width:575px){.nx-gas-row{grid-template-columns:82px 1fr 65px;font-size:.85rem}.nx-demo-navigation .btn{min-width:0}.nx-back-link{font-size:.8rem}}