.world-page section { padding-block: clamp(48px, 5vw, 72px); scroll-margin-top: 85px; }
.world-page .world-hero { --world-gutter: clamp(20px, 3.3vw, 64px); padding-block: clamp(24px, 2vw, 38px) 28px; text-align: center; }
.world-page .world-hero > .wrap { width: 100%; max-width: none; padding-inline: 0; }
.world-page .world-hero h1 { max-width: min(1600px, calc(100% - 2 * var(--world-gutter))); margin: 0 auto; font-size: clamp(32px, 3.45vw, 56px); line-height: 1.1; text-wrap: balance; }
:lang(zh) .world-page .world-hero h1 { line-height: 1.2; word-break: normal; }
.world-page .world-subtitle { margin: 12px var(--world-gutter) clamp(18px, 1.4vw, 26px); color: var(--vi-n217); font-size: clamp(17px, 1.7vw, 25px); line-height: 1.45; }
.world-page video, .world-page figure img { display: block; width: 100%; height: auto; object-fit: contain; border-radius: 12px; }
.world-page video { background: var(--vi-n11); }
.world-page .world-film { width: 100%; max-width: none; aspect-ratio: 16 / 9; margin: 0; border-radius: 0; }
.world-scenes > .wrap, .world-physics > .wrap { max-width: 1760px; padding-inline: clamp(20px, 3.3vw, 64px); }
.world-jumps { display: flex; flex-wrap: wrap; justify-content: center; column-gap: 32px; row-gap: 4px; margin-top: 18px; }
.world-jumps a { padding-block: 9px; color: var(--vi-brand); font-size: 14px; text-decoration: none; }
.world-jumps a::after { content: ' ↓'; padding-left: 8px; }
.world-jumps a:hover { text-decoration: underline; text-underline-offset: 5px; }
.world-page .world-heading { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(24px, 4vw, 64px); align-items: start; margin-bottom: clamp(24px, 2.5vw, 34px); }
.world-page .world-heading h2 { max-width: 100%; font-size: clamp(30px, 3.1vw, 48px); line-height: 1.16; text-wrap: balance; }
.world-page .world-heading p, .world-page .physics-notes p, .world-page .world-edit p, .world-page .world-close p { margin: 0; line-height: 1.75; }
.world-page figure { margin: 0; min-width: 0; }
.world-page figcaption { position: static; background: none; margin: 12px 0 0; padding: 0; color: var(--gray-600); font-size: 14px; font-weight: 400; line-height: 1.6; }
.world-page .scene-hint { font-size: 14px; color: var(--gray-600); margin: 0 0 14px; }
.scene-selector { display: grid; grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 10px; margin-bottom: 18px; }
.scene-choice { display: grid; grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr); align-items: center; gap: 5px; padding: 5px; border: 1px solid var(--vi-n217); border-radius: 10px; background: var(--vi-n255); color: var(--vi-n77); cursor: pointer; font: inherit; min-width: 0; text-align: left; transition: border-color .15s, background .15s; }
.scene-choice img { width: 100%; height: auto; aspect-ratio: 3 / 2; border-radius: 6px; }
.scene-choice span { display: block; padding: 4px; font-size: 14px; line-height: 1.3; font-weight: 600; }
.scene-choice:hover { border-color: var(--vi-n118); background: var(--vi-n245); }
.scene-choice[aria-pressed="true"] { border-color: var(--vi-n92); box-shadow: 0 0 0 1px var(--vi-n92); background: var(--vi-n245); color: var(--vi-n51); }
.world-page button:focus-visible, .world-page a:focus-visible, .world-page summary:focus-visible { outline: 3px solid var(--vi-n118); outline-offset: 5px; }
.scene-viewer { padding: clamp(20px, 1.5vw, 24px); background: var(--vi-n23); color: var(--vi-n255); border-radius: 16px; }
.scene-context { margin-top: 22px; }
.world-page .scene-context h3 { font-size: 26px; line-height: 1.2; margin: 0 0 12px; }
.world-page .scene-context p { margin: 0; font-size: 15px; line-height: 1.65; color: var(--vi-n217); max-width: 33ch; }
.scene-comparison { display: grid; grid-template-columns: minmax(220px, .85fr) minmax(0, 2.75fr); gap: clamp(20px, 2vw, 32px); align-items: start; }
.world-page .scene-comparison figcaption { color: var(--vi-n217); font-size: 13px; margin: 0 0 12px; }
.world-page .scene-comparison img, .world-page .scene-comparison video { aspect-ratio: 3 / 2; border-radius: 8px; }
.scene-chapters { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 10px; margin-top: 16px; }
.scene-chapters button { color: var(--vi-n217); background: none; border: 0; border-top: 2px solid var(--vi-n92); padding: 13px 2px 8px; font: inherit; font-size: 14px; line-height: 1.4; text-align: left; cursor: pointer; min-height: 48px; }
.scene-chapters button[aria-current="step"] { color: var(--vi-brand); border-color: var(--vi-brand); }
.scene-chapters button:hover { color: var(--vi-n255); border-color: var(--vi-n255); }
.world-overview { margin-top: 10px; border-bottom: 1px solid var(--vi-n217); }
.world-overview summary { cursor: pointer; padding-block: 16px 18px; font-weight: 600; font-size: 15px; }
.overview-duration { margin-left: 12px; color: var(--gray-600); font-weight: 400; font-size: 13px; }
.world-overview video { margin-bottom: 28px; aspect-ratio: 1920 / 868; }
.physics-layout { display: grid; grid-template-columns: minmax(0, 2.6fr) minmax(0, 1fr); gap: clamp(28px,3vw,48px); }
.physics-layout video { aspect-ratio: 16 / 9; }
.physics-notes article { padding: 18px 0; border-top: 1px solid var(--vi-n217); }
.physics-notes article:first-child { padding-top: 0; border: 0; }
.world-page .physics-notes h3, .world-page .world-edit h3, .world-page .world-close h3 { font-size: clamp(21px, 2vw, 28px); line-height: 1.25; margin: 0 0 12px; }
.world-page .physics-notes p { color: var(--gray-600); font-size: 15px; }
.world-edit { display: grid; grid-template-columns: minmax(0, .85fr) minmax(0, 1.7fr); align-items: center; gap: clamp(28px,4vw,64px); margin-top: clamp(36px,4vw,56px); padding-top: clamp(32px,3.5vw,48px); border-top: 1px solid var(--vi-n217); }
.world-edit video { aspect-ratio: 16 / 9; }
.world-page .world-edit p { color: var(--gray-600); }
.world-page .world-close { display: flex; gap: 28px; align-items: center; justify-content: space-between; margin-top: clamp(36px,4vw,56px); padding-top: clamp(32px,4vw,48px); border-top: 1px solid var(--vi-n217); }
.world-close p { color: var(--gray-600); }
.world-close a { flex: none; }
@media (max-width: 900px) {
  .world-page .world-heading { grid-template-columns: 1fr; gap: 20px; }
  .world-page .world-heading h2 { max-width: 24ch; }
  .scene-selector { grid-template-columns: repeat(3,minmax(0,1fr)); }
  .scene-choice { grid-template-columns: minmax(0,1fr) minmax(0,1fr); }
  .scene-context { margin-top: 18px; }
  .scene-comparison { grid-template-columns: minmax(0,1fr) minmax(0,2fr); gap: 20px; }
  .physics-layout { grid-template-columns: 1fr; }
  .physics-notes { display: grid; grid-template-columns: repeat(3,minmax(0,1fr)); gap: 24px; }
  .physics-notes article, .physics-notes article:first-child { padding: 18px 0 0; border-top: 1px solid var(--vi-n217); }
}
@media (max-width: 600px) {
  .world-page section { padding-block: 44px; }
  .world-page .world-hero { padding-block: 24px; }
  .world-page .world-hero h1 { font-size: 30px; }
  .world-jumps { column-gap: 20px; }
  .scene-selector { grid-template-columns: repeat(3, minmax(0,1fr)); gap: 10px; margin-bottom: 20px; }
  .scene-choice { display: flex; flex-direction: column; gap: 0; padding: 4px; }
  .scene-choice span { padding: 6px 3px 3px; font-size: 13px; }
  .world-scenes > .wrap, .world-physics > .wrap { padding-inline: 20px; }
  .scene-viewer { margin-inline: -20px; padding: 20px 0 12px; border-radius: 0; }
  .scene-context { margin: 0; }
  .world-page .scene-context h3 { font-size: 20px; margin-bottom: 8px; }
  .world-page .scene-context p { font-size: 13px; line-height: 1.6; }
  .scene-comparison { grid-template-columns: 1fr; gap: 24px; }
  .scene-input { display: grid; grid-template-columns: minmax(0,1fr) minmax(0,1.2fr); gap: 0 14px; align-items: start; padding-inline: 20px; }
  .scene-input figcaption { grid-column: 1 / -1; }
  .scene-chapters { gap: 8px; margin: 12px 20px 0; }
  .scene-output > figcaption { padding-inline: 20px; }
  .world-page .scene-output video { border-radius: 0; }
  .scene-chapters button { font-size: 12px; }
  .world-page .scene-comparison figcaption { margin-bottom: 10px; }
  .world-overview summary { font-size: 14px; }
  .overview-duration { white-space: nowrap; }
  .physics-notes { grid-template-columns: 1fr; gap: 22px; }
  .world-page .physics-layout > figure > video, .world-page .world-edit > video, .world-page .world-overview > video { width: calc(100% + 40px); max-width: none; margin-inline: -20px; border-radius: 0; }
  .world-edit { grid-template-columns: 1fr; gap: 24px; }
  .world-page .world-close { flex-direction: column; align-items: flex-start; gap: 24px; }
}
@media (prefers-reduced-motion: reduce) { .scene-choice { transition: none; } }

/* Research follows the demonstrations as a separate reading section. */
.world-research { background: var(--vi-n255); }
.research-heading { max-width: 850px; }
.world-page .research-eyebrow { margin: 0 0 14px; color: var(--vi-n92); font-size: 13px; font-weight: 600; letter-spacing: .08em; }
.world-page .research-heading h2 { max-width: 25ch; font-size: clamp(30px,3.1vw,46px); line-height: 1.18; text-wrap: balance; }
.world-page .research-heading > p:last-child { margin: 22px 0 0; max-width: 75ch; line-height: 1.8; color: var(--gray-600); }
.research-nav { display: flex; flex-wrap: wrap; gap: 10px 30px; margin: 28px 0 36px; }
.research-nav a { padding-block: 8px; color: var(--vi-n92); text-decoration: none; font-size: 14px; font-weight: 600; }
.research-nav a::after { content: ' ↓'; font-weight: 400; }
.research-nav a:hover { text-decoration: underline; text-underline-offset: 5px; }
.research-entry { display: grid; grid-template-columns: minmax(0, .85fr) minmax(0, 2fr); gap: clamp(30px,5vw,68px); padding-block: 40px; border-top: 1px solid var(--vi-n217); scroll-margin-top: 100px; }
.research-number { display: block; color: var(--vi-n92); font-size: 13px; font-weight: 600; margin-bottom: 14px; }
.world-page .research-entry h3 { margin: 0; font-size: clamp(23px,2.1vw,30px); line-height: 1.3; text-wrap: balance; }
.research-content { min-width: 0; }
.world-page .research-content > p { margin: 0; font-size: 16px; line-height: 1.8; }
.research-papers { display: flex; flex-wrap: wrap; gap: 12px 24px; margin-top: 18px; }
.research-papers a { color: var(--vi-n92); font-size: 14px; font-weight: 600; text-decoration: underline; text-underline-offset: 5px; }
.world-page .research-figure { margin-top: 26px; }
.world-page .research-figure > a { display: block; padding: 14px; border: 1px solid var(--vi-n217); border-radius: 10px; background: var(--vi-n255); }
.world-page .research-figure img { border-radius: 0; }
.world-page .research-figure figcaption { font-size: 12px; line-height: 1.7; margin-top: 12px; }
.research-figure figcaption a { color: var(--vi-n92); white-space: nowrap; text-underline-offset: 3px; }
.world-page .research-figure-parts { max-width: 600px; }
.world-page .research-content .research-note { margin-top: 18px; font-size: 14px; color: var(--gray-600); line-height: 1.75; }
.research-more { margin-top: 22px; border-top: 1px solid var(--vi-n217); }
.research-more summary { padding: 15px 0; color: var(--vi-n92); font-size: 14px; cursor: pointer; }
.world-page .research-more .research-figure { margin-top: 8px; }
.validation-steps { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 26px 30px; list-style: none; padding: 0; margin: 28px 0 0; }
.validation-steps li { border-top: 2px solid var(--vi-n189); padding-top: 17px; }
.world-page .validation-steps h4 { margin: 0 0 9px; font-size: 17px; line-height: 1.45; }
.world-page .validation-steps p { margin: 0; color: var(--gray-600); font-size: 14px; line-height: 1.8; }
.research-library { border-top: 1px solid var(--vi-n217); padding-top: 28px; }
@media (max-width: 800px) {
  .research-entry { grid-template-columns: 1fr; gap: 22px; padding-block: 32px; }
  .research-entry header { max-width: 620px; }
  .research-number { margin-bottom: 10px; }
  .research-nav { gap: 8px 22px; margin-bottom: 24px; }
}
@media (max-width: 480px) {
  .world-page .research-heading > p:last-child { margin-top: 18px; font-size: 15px; }
  .world-page .research-content > p { font-size: 15px; }
  .world-page .research-figure > a { padding: 8px; }
  .validation-steps { grid-template-columns: 1fr; gap: 22px; }
}