/* Concept explanations for Lecture 01; dimensions follow the 1920 × 1080 deck. */
.reveal .concept-slide { --concept-accent:var(--c-stat); text-align:left; }
.reveal .concept-slide.comp { --concept-accent:var(--c-comp); }
.reveal .concept-slide.cyber { --concept-accent:var(--c-cyber); }
.reveal .concept-slide.neural { --concept-accent:var(--c-neural); }
.reveal .concept-slide .slide-body { gap:28px; position:relative; }
.reveal .concept-slide h2 { font-size:58px; line-height:1.15; margin:0; text-transform:none; }
.reveal .concept-slide p { font-size:32px; line-height:1.4; margin:0; }
.reveal .concept-slide .concept-lead { color:var(--text-muted); }
.reveal .concept-grid { display:grid; grid-template-columns:repeat(2,minmax(0,1fr)); gap:26px; }
.reveal .concept-grid.three { grid-template-columns:repeat(3,minmax(0,1fr)); }
.reveal .concept-card { padding:28px; border:1px solid var(--line); border-top:4px solid var(--concept-accent); border-radius:14px; background:var(--bg-elevated); }
.reveal .concept-card h3 { font-size:30px; color:var(--concept-accent); margin:0 0 16px; text-transform:none; }
.reveal .concept-card p + p { margin-top:16px; }
.reveal .concept-slide sup { font-size:.7em; line-height:0; vertical-align:super; }
.reveal .concept-equation { padding:28px; background:var(--bg-elevated); border:1px solid var(--line); border-radius:14px; font-size:44px; text-align:center; line-height:1.45; }
.reveal .concept-equation small { display:block; font:27px/1.5 'Segoe UI',Arial,sans-serif; color:var(--text-muted); margin-top:12px; }
.reveal .concept-fraction { display:inline-flex; flex-direction:column; vertical-align:middle; text-align:center; margin:0 12px; }
.reveal .concept-fraction > :first-child { border-bottom:2px solid var(--concept-accent); padding:0 16px 8px; }
.reveal .concept-fraction > :last-child { padding-top:8px; }
.reveal .concept-takeaway { border-left:5px solid var(--concept-accent); padding:16px 24px; background:rgba(255,255,255,.035); }
.reveal .concept-slide .concept-links { display:flex; gap:26px; font-size:22px; margin-top:8px; }
.reveal .concept-links a { color:var(--text-muted); text-decoration:underline; text-underline-offset:5px; }
.reveal .concept-slide a:focus-visible { outline:3px solid #ffd166; outline-offset:5px; }
.reveal .concept-flow { display:flex; align-items:stretch; gap:18px; }
.reveal .concept-flow .concept-card { flex:1; min-width:0; }
.reveal .concept-arrow { align-self:center; color:var(--concept-accent); font-size:42px; }
.reveal .concept-table { width:100%; margin:0; font-size:30px; border-collapse:collapse; }
.reveal .concept-table th,.reveal .concept-table td { padding:18px 26px; border-bottom:1px solid var(--line); text-align:left; }
.reveal .concept-table th { color:var(--concept-accent); }
.reveal .concept-table .total { background:rgba(69,214,192,.09); }
.reveal .concept-slide .concept-small { font-size:26px; color:var(--text-muted); }
.reveal .concept-plot { width:100%; height:340px; display:block; background:var(--bg-elevated); border-radius:14px; }
.reveal .concept-index a { display:block; color:var(--text); font-size:29px; line-height:1.35; margin:16px 0 0; text-decoration:underline; text-underline-offset:5px; }
.reveal .concept-slide code { color:var(--concept-accent); }

/* Era II introductions retain their historical media alongside the core idea. */
.reveal .era-focus .era-layout { display:grid; grid-template-columns:480px minmax(0,1fr); gap:60px; align-items:center; }
.reveal .era-focus .era-media { margin:0; }
.reveal .era-focus .era-explanation { display:flex; flex-direction:column; gap:24px; }
.reveal .era-focus .era-steps { list-style:none; margin:0; padding:0; display:grid; gap:20px; }
.reveal .era-focus .era-steps li { margin:0; font-size:31px; line-height:1.4; padding-left:24px; border-left:3px solid var(--concept-accent); }
.reveal .era-focus .era-steps strong { color:var(--concept-accent); }
.reveal .era-focus .era-media .video-links { font-size:22px; margin-top:12px; }
.reveal .era-focus .test-channel { text-align:center; color:var(--concept-accent); }
.reveal .era-focus .test-examiner { text-align:center; }
.reveal .era-focus .test-examiner h3 { margin-bottom:10px; }
.reveal .turing-machine-diagram { display:block; width:100%; height:540px; }