/* A clear reading path: choose, locate, understand, explore. */
.movement-page .physics-chapter[hidden]{display:none!important}
.physics-chapters{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:8px 0 26px}
.physics-chapters button{display:flex;align-items:center;gap:16px;min-height:88px;padding:18px 20px;border:1px solid #bfcbbc;background:#fffef9;color:#294b3f;text-align:left;border-radius:12px;font:inherit;cursor:pointer}
.physics-chapters button>span{font:400 1.5rem Georgia,serif;color:#8c6a36}
.physics-chapters strong,.physics-chapters small{display:block;line-height:1.45}
.physics-chapters strong{font-size:1.05rem}.physics-chapters small{font-size:.875rem;margin-top:4px;color:#536b5e}
.physics-chapters button[aria-pressed=true]{background:#244638;border-color:#244638;color:#fffef8;box-shadow:inset 0 -3px #bd9958}
.physics-chapters button[aria-pressed=true]>span{color:#e7c788}.physics-chapters button[aria-pressed=true] small{color:#e0e7dd}
.physics-chapters button:focus-visible,.physics-classroom button:focus-visible{outline:3px solid #af8541;outline-offset:3px}
.physics-topic-groups{display:grid;grid-template-columns:1.3fr 1fr 1fr;gap:22px;padding:24px;border-top:1px solid #d4ddcd}
.physics-topic-groups h3{margin:0 0 14px;font-size:1rem;font-weight:650;color:#536b5e;line-height:1.5}
.physics-topic-groups .movement-topic-nav{display:grid;grid-template-columns:1fr;gap:6px;padding:0}
.physics-topic-groups .movement-topic-nav button{padding:12px 14px;min-height:62px;border-radius:7px;text-align:left}
.physics-topic-groups .movement-topic-nav strong{font-size:1rem}.physics-topic-groups .movement-topic-nav small{font-size:.875rem;line-height:1.5}
.physics-classroom{overflow:hidden;border:1px solid #cbd6c6;border-radius:16px;background:#fffef9;margin-top:24px;color:#254638}
.physics-classroom>header{padding:clamp(22px,3vw,42px) clamp(22px,4vw,48px) 24px;max-width:1000px}
.physics-classroom .eyebrow{font-size:.875rem;letter-spacing:.06em;color:#876635;font-weight:650}
.physics-classroom h2{font:500 clamp(1.8rem,3vw,2.75rem)/1.16 Georgia,serif;margin:14px 0 20px;max-width:860px;letter-spacing:-.025em}
.physics-classroom .classroom-definition{font-size:1.125rem;line-height:1.75;margin:0;max-width:840px;color:#345444}
.classroom-location{display:grid;grid-template-columns:1fr 1fr;gap:30px;padding:24px clamp(22px,4vw,48px);background:#f0f3ec;border-block:1px solid #d6dfcf}
.classroom-location span{font-size:.875rem;font-weight:650;letter-spacing:.055em;color:#5b6d50}.classroom-location p{font-size:1rem;line-height:1.65;margin:8px 0 0}
.classroom-timeline{display:flex;flex-wrap:wrap;list-style:none;margin:0;padding:20px clamp(22px,4vw,48px);gap:7px}
.classroom-timeline li{font-size:.875rem;line-height:1.5;padding:6px 11px;border-radius:5px;color:#6a756c;background:#f5f6f0}
.classroom-timeline li.is-active{background:#294b3f;color:#fffef7}
.classroom-figure{margin:0;padding:0 clamp(18px,3vw,32px) 24px}
.classroom-photo{position:relative;overflow:hidden;border-radius:10px;background:#e8ece5}
.classroom-photo-canvas{position:relative}.classroom-photo-canvas>img{display:block;width:100%;height:auto}
.classroom-photo-feet,.classroom-photo-impact{max-width:780px;margin:auto}
.classroom-photo-labels{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px;padding:17px 0 0}
.classroom-photo-labels span{display:flex;align-items:center;gap:9px;font-size:.9375rem;font-weight:650;color:#2c4f3f}
.classroom-photo-labels b{flex:0 0 27px;height:27px;display:grid;place-items:center;border:1px solid #bdcaba;border-radius:50%;font-size:.875rem}
.classroom-figure figcaption>p{font-size:.875rem;margin:12px 0;color:#58705e;line-height:1.5}
.classroom-photo-explanations{border-top:1px solid #d0dacb}
.classroom-photo-note{display:block;font-size:.875rem;line-height:1.6;color:#64735e;margin-top:16px}
.classroom-example{display:grid;grid-template-columns:1.2fr 1fr;gap:32px;padding:28px clamp(22px,4vw,48px);border-top:1px solid #d8dfd1}
.classroom-example h3{font-size:1.4rem;line-height:1.3;margin:10px 0 16px;max-width:600px}.classroom-example p{font-size:1rem;line-height:1.75;margin:10px 0 0;color:#3e584a}
.classroom-example aside{padding-left:28px;border-left:1px solid #cbd5c4}.classroom-example aside>strong{font-size:1.05rem;line-height:1.5;display:block}
.classroom-mistake{margin:0 clamp(22px,4vw,48px) 28px;padding:18px 22px;background:#f4edde;border-left:3px solid #b78b43;border-radius:0 7px 7px 0}
.classroom-mistake strong{font-size:1rem;color:#775830}.classroom-mistake p{font-size:1rem;line-height:1.7;margin:7px 0 0;color:#5a5946}
.classroom-continue{padding:18px clamp(22px,4vw,48px);margin:0;font-size:.9375rem;color:#62735c;background:#f6f7f1;border-top:1px solid #e0e6d8}
.physics-lesson-fold,.physics-teacher-method{border:1px solid #cbd6c6;background:#fffef9;border-radius:12px;margin:14px 0;overflow:hidden}
.physics-lesson-fold>summary,.physics-teacher-method>summary{list-style:none;display:flex;align-items:center;gap:18px;cursor:pointer;min-height:78px;padding:18px 24px;color:#294b3f;font-size:1.125rem;font-weight:650}
.physics-lesson-fold>summary::-webkit-details-marker,.physics-teacher-method>summary::-webkit-details-marker{display:none}
.physics-lesson-fold>summary>span{font:400 1.6rem Georgia,serif;color:#937541}
.physics-lesson-fold>summary::after,.physics-teacher-method>summary::after{content:'+';font-size:1.6rem;font-weight:400;margin-left:auto}
.physics-lesson-fold[open]>summary::after,.physics-teacher-method[open]>summary::after{content:'−'}
.physics-lesson-fold>summary small{display:block;font-size:.875rem;font-weight:400;color:#60735e;line-height:1.5;margin-top:5px}
.physics-lesson-fold>summary:focus-visible,.physics-teacher-method>summary:focus-visible{outline:3px solid #b48743;outline-offset:-3px}
.physics-teacher-method .movement-method{margin:0;border:0}
.physics-chapter>.newton-section,.physics-chapter>.contact-lesson{margin:0;border:1px solid #cbd6c6;border-radius:16px;background:#fffef9;padding:clamp(20px,3vw,36px)}
.physics-chapter .newton-example{grid-template-columns:1fr}
.physics-chapter .newton-explanation{max-width:1000px;padding:4px 10px 0}.physics-chapter .newton-location{grid-template-columns:1fr 1fr}
.physics-chapter .newton-visual>.classroom-figure{padding:0}
.physics-chapter .newton-visual .classroom-photo-feet{max-width:850px}
.physics-chapter .newton-visual-caption{border-radius:7px;margin-top:16px}
.physics-chapter .newton-practice{margin-top:24px}
@media(max-width:750px){.physics-chapters{gap:7px}.physics-chapters button{padding:12px 10px;display:block;min-height:118px}.physics-chapters button>span{font-size:1.15rem;display:block;margin-bottom:7px}.physics-chapters strong{font-size:.9375rem}.physics-chapters small{font-size:.875rem}.physics-topic-groups{grid-template-columns:1fr;padding:18px;gap:20px}.classroom-location,.classroom-example{grid-template-columns:1fr;gap:20px}.classroom-example aside{border-left:0;border-top:1px solid #cbd5c4;padding:20px 0 0}.classroom-photo-labels{gap:8px}.classroom-photo-labels span{font-size:.875rem;align-items:flex-start}.classroom-photo-labels b{flex-basis:22px;height:22px}.physics-classroom .classroom-definition{font-size:1rem}.physics-chapter .newton-location{grid-template-columns:1fr}.physics-lesson-fold>summary{padding:17px 18px;font-size:1rem;gap:13px}}
@media(max-width:440px){.physics-chapters{grid-template-columns:1fr}.physics-chapters button{min-height:64px;display:flex;padding:13px 16px}.physics-chapters button>span{margin:0;flex-basis:24px}.physics-chapters small{margin-top:1px}.classroom-photo-swing .physics-point{width:34px;height:34px;font-size:1rem;min-height:34px}.classroom-photo-labels{grid-template-columns:1fr}.classroom-photo-labels span{align-items:center}.classroom-timeline{gap:5px}.classroom-timeline li{padding:5px 8px}}
.newton-focus{padding:20px 24px;margin-bottom:20px;border-left:3px solid #b78b43;background:#f1f4ed;border-radius:0 9px 9px 0}.newton-focus strong{font-size:1.125rem;color:#294b3f}.newton-focus p{margin:7px 0 0;font-size:1rem}

.classroom-pan-hint{display:none}.movement-page .movement-entry{padding:8px 0;background:transparent;border:0;box-shadow:none}.movement-page .movement-entry button{background:transparent;color:#3b5d49;padding:7px 0;text-decoration:underline;text-underline-offset:4px;font-size:.9375rem}.movement-page .movement-entry>span{font-size:.875rem}
@media(max-width:750px){.classroom-photo-swing{overflow-x:auto;overscroll-behavior-x:contain;scrollbar-width:thin}.classroom-photo-swing .classroom-photo-canvas{min-width:840px}.classroom-figure figcaption>.classroom-pan-hint{display:block;color:#725932}.classroom-photo-swing:focus-visible{outline:3px solid #b78b43;outline-offset:2px}}
.classroom-force-overlay{position:absolute;inset:0;width:100%;height:100%;pointer-events:none}.newton-vector-legend{display:flex;flex-wrap:wrap;gap:10px 24px;background:#edf2eb;padding:18px 22px;border-radius:8px}.newton-vector-legend>span{font-size:1rem;font-weight:600}.newton-vector-legend>small{flex-basis:100%;font-size:.875rem;line-height:1.6;color:#5a6d5e}
/* Keep the notebook available without pushing the mobile header outside the screen. */
@media(max-width:440px){.topbar .notebook-link{min-width:44px;min-height:44px;padding:8px;justify-content:center}.topbar .notebook-link>span{position:absolute;clip-path:inset(50%);width:1px;height:1px;overflow:hidden;white-space:nowrap}}

/* Keep teaching vectors legible against the dark driver photograph. */
.classroom-photo-impact .classroom-force-overlay,[data-movement-photo="collision"] .movement-physics-overlay{filter:drop-shadow(0 0 1px #fffef7) drop-shadow(0 0 2px #fffef7)}