.hidden{display:none!important}.lesson-header{height:78px;padding:0 max(24px,calc((100% - 1180px)/2));display:grid;grid-template-columns:1fr minmax(260px,420px) 1fr;align-items:center;gap:20px;position:sticky;top:0;z-index:30}.exit-link{justify-self:end;color:var(--ink-soft);font-size:10px}.lesson-progress{display:flex;align-items:center;gap:12px;color:var(--ink-soft);font-size:9px}.lesson-progress i{flex:1;height:6px;background:#e4eaec;border-radius:999px;overflow:hidden}.lesson-progress b{display:block;width:20%;height:100%;background:linear-gradient(90deg,var(--blue-dust),var(--sage));transition:width .3s}.lesson-shell{min-height:calc(100vh - 78px);display:grid;grid-template-columns:.94fr 1.06fr}.scene-panel{position:relative;overflow:hidden;min-height:calc(100vh - 78px);background:url("images/hero-inference.png") center/cover no-repeat;color:white}.scene-panel:before{content:"";position:absolute;inset:0;background:linear-gradient(90deg,rgba(43,67,86,.32),rgba(43,67,86,.08)),linear-gradient(0deg,rgba(43,67,86,.20),transparent 55%)}.scene-copy{position:absolute;left:clamp(28px,5vw,68px);right:42px;bottom:70px;z-index:2}.scene-copy blockquote{max-width:590px;margin:15px 0 22px;color:#fffdf7;font:500 clamp(31px,3.7vw,48px)/1.13 Georgia,serif}.scene-copy p{max-width:520px;margin:0;color:#e9ddc8;font:italic 17px/1.65 Georgia,serif}.eyebrow.light{color:#d8e3e7}.lesson-panel{position:relative;padding:58px clamp(28px,5vw,70px);background:radial-gradient(circle at 91% 9%,rgba(166,190,204,.16),transparent 22%),linear-gradient(180deg,#fffdf8,#faf6ee)}.lesson-stage{max-width:650px;margin:0 auto}.lesson-stage h1{margin:8px 0 15px;font:500 clamp(37px,4vw,52px)/1.04 Georgia,serif}.lesson-stage h2{margin:30px 0 16px;font:500 24px/1.3 Georgia,serif}.lesson-copy{color:var(--ink-soft);font:14px/1.75 Georgia,serif}.sentence-card{position:relative;margin:28px 0;padding:20px;border:1px solid var(--line);border-radius:15px;background:radial-gradient(circle at 14% 18%,rgba(205,222,231,.31),transparent 22%),rgba(249,247,240,.95);box-shadow:var(--shadow-soft)}.sentence-card p{margin:0;font:15px/1.78 Georgia,serif}.choice-grid{display:grid;gap:10px}.choice-grid button{padding:14px 16px;border:1px solid var(--line);border-radius:13px;background:rgba(255,253,249,.94);text-align:left}.choice-grid button:hover{transform:translateY(-1px);border-color:rgba(111,143,167,.42)}.feedback{margin-top:16px;padding:14px 16px;border-radius:12px;font-size:11px;line-height:1.65}.feedback.good{background:#e8efe9;color:#526b5b}.feedback.try{background:#f3e9df;color:#745f46}.answer-builder{display:grid;gap:10px;margin:25px 0}.answer-builder>div{padding:16px;border-left:3px solid var(--gold);border-radius:0 13px 13px 0;background:#faf4ea}.answer-builder span,.completion-card span{display:block;color:var(--blue-dust);font-size:8px;font-weight:850;letter-spacing:.09em}.answer-builder p{margin:5px 0 0;font:14px/1.6 Georgia,serif}.completion-card{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin:28px 0}.completion-card>div{padding:18px;border:1px solid var(--line);border-radius:14px;background:#edf3ef}.completion-card strong{display:block;margin-top:6px;font:500 18px Georgia,serif}.final-actions{display:flex;flex-wrap:wrap;gap:8px;margin-top:24px}@media(max-width:850px){.lesson-header{grid-template-columns:1fr auto}.lesson-progress{display:none}.lesson-shell{grid-template-columns:1fr}.scene-panel{min-height:520px}.completion-card{grid-template-columns:1fr}}