@font-face { font-family: DM Sans; src: url('assets/dm-sans.ttf') format('truetype'); font-weight: 100 1000; font-display: swap; }
@font-face { font-family: Be Vietnam Pro; src: url('assets/be-vietnam-pro-bold.ttf') format('truetype'); font-weight: 700; font-display: swap; }
:root {
  --orange: #e8611a; --orange-ink: #c9500f; --ink: #1c1d21; --muted: #55524e; --soft: #6d6a66;
  --line: #d8d2ca; --paper: #f4f1ec; --card: #fffdfa; --tint: #fdeee4;
  --zoom: 900ms; --fade: 520ms;
  color-scheme: light; font-family: DM Sans, sans-serif; color: var(--ink); background: var(--paper);
}
* { box-sizing: border-box; }
body { margin: 0; min-width: 320px; background: var(--paper); }
button { font: inherit; color: inherit; cursor: pointer; }
a { color: inherit; text-decoration: none; }
:focus-visible { outline: 2px solid var(--orange); outline-offset: 3px; }
[hidden] { display: none !important; }
h1, h2, h3, p { margin-top: 0; }
.skip-link { position: absolute; top: -55px; left: 10px; z-index: 30; padding: 12px; background: var(--ink); color: white; }
.skip-link:focus { top: 8px; }
.preview-flag { display: flex; align-items: center; justify-content: center; gap: 10px; min-height: 28px; background: var(--orange); color: #15171a; font-size: 10px; font-weight: 900; letter-spacing: .16em; }
.preview-flag span { opacity: .5; }
.site-header { display: flex; align-items: center; max-width: 1550px; min-height: 78px; margin: auto; padding: 0 3vw; border-bottom: 1px solid var(--line); }
.brand img { display: block; width: 184px; height: auto; }
.header-kicker { margin-left: auto; color: var(--soft); font-size: 10px; font-weight: 800; letter-spacing: .18em; }
.header-kicker b { color: var(--orange-ink); }

.section { max-width: 1550px; margin: auto; padding: 0 3vw 56px; }
.intro { display: grid; grid-template-columns: minmax(0, 1.9fr) minmax(0, 1fr); align-items: end; gap: 50px; padding: 50px 0 32px; }
.eyebrow { display: flex; align-items: center; gap: 12px; margin-bottom: 22px; color: var(--orange-ink); font-size: 11px; font-weight: 900; letter-spacing: .16em; }
.eyebrow span { width: 23px; height: 2px; background: var(--orange); }
h1 { margin: 0; font: 700 clamp(28px, 3.4vw, 54px)/1.08 Be Vietnam Pro, sans-serif; letter-spacing: -.055em; }
h1 span, h1 em { display: block; white-space: nowrap; }
h1 em { color: var(--orange); font-style: normal; }
.intro-copy { max-width: 560px; margin: 0; color: var(--muted); font-size: clamp(15px, 1.35vw, 18px); line-height: 1.62; }

/* The overview and the beginner guide share one row on desktop. */
.explore { display: grid; grid-template-columns: minmax(0, 1.86fr) minmax(318px, .86fr); gap: 14px; align-items: stretch; }

/* Stage: always a photo, so its controls stay dark. */
.stage { position: relative; border: 1px solid #cfc8bf; background: #0b0c0f; }
.viewport { position: relative; aspect-ratio: 2048 / 1360; overflow: hidden; }
.overview, .shot { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; display: block; user-select: none; -webkit-user-drag: none; }
.overview { opacity: 0; transform-origin: var(--ox, 50%) var(--oy, 50%); transition: transform var(--zoom) cubic-bezier(.7, 0, .2, 1), filter var(--zoom) ease, opacity var(--fade) ease; }
.stage[data-scene='day'] .overview[data-scene='day'], .stage[data-scene='night'] .overview[data-scene='night'] { opacity: 1; }
.stage[data-state='zoom'] .overview { transform: scale(2.7); filter: brightness(.75) blur(2px); }
.shot { opacity: 0; transform: scale(1.06); transition: opacity var(--fade) ease, transform 6s ease-out; pointer-events: none; }
.shot.on { opacity: 1; transform: scale(1); }
.viewport.pointing { cursor: zoom-in; }

/* Glow that follows the item's own outline: a copy of the photo cut by the item mask, lifted over a dimmed scene. */
.stage { --light-fade: 280ms; --light-ease: cubic-bezier(.4, 0, .2, 1); }
.stage.sweeping { --light-fade: 760ms; }
.dim { position: absolute; inset: 0; background: rgba(7, 8, 10, .5); opacity: 0; transition: opacity 760ms var(--light-ease); pointer-events: none; }
.spotlight { position: absolute; inset: 0; opacity: 0; transition: opacity var(--light-fade) var(--light-ease); pointer-events: none; }
.spotlight.on { opacity: 1; }
.glow { position: absolute; inset: 0; pointer-events: none;
  filter: drop-shadow(0 0 2px rgba(255, 190, 150, .75)) drop-shadow(0 0 12px rgba(232, 97, 26, .55)) drop-shadow(0 0 28px rgba(232, 97, 26, .25)); }
.lit { position: absolute; inset: 0; background: var(--scene-img) center / 100% 100% no-repeat; filter: brightness(1.1) saturate(1.05);
  -webkit-mask: var(--mask) center / 100% 100% no-repeat; mask: var(--mask) center / 100% 100% no-repeat; }
.stage.lighting .dim { opacity: 1; }
.stage.sweeping.lighting .dim { opacity: .48; }
.stage[data-scene='night'] .dim { background: rgba(0, 0, 0, .55); }
.stage[data-scene='day'] .glow { filter: drop-shadow(0 0 2px rgba(232, 97, 26, .7)) drop-shadow(0 0 11px rgba(232, 97, 26, .5)) drop-shadow(0 0 26px rgba(232, 97, 26, .22)); }
.stage[data-state='zoom'] .dim, .stage[data-state='zoom'] .spotlight { opacity: 0 !important; }
.spot-name { position: absolute; padding: 6px 10px; background: #f5efe9; color: #15171a; font-size: 10px; font-weight: 900; letter-spacing: .1em; white-space: nowrap; opacity: 0; transition: opacity 180ms ease; transform: translate(0, -100%) translateY(-8px); pointer-events: none; }
.spotlight.on .spot-name { opacity: 1; transition-delay: 120ms; }
.spot-name.below { transform: translateY(8px); }
.spot-name::before { display: inline-block; width: 6px; height: 6px; margin-right: 7px; border-radius: 50%; background: var(--orange); content: ''; vertical-align: 1px; }
/* Keyboard access: one invisible button per item, lights the item on focus. */
.spot-keys button { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0 0 0 0); border: 0; }

.scene-switch { position: absolute; top: 12px; right: 12px; display: flex; padding: 3px; border: 1px solid rgba(255, 255, 255, .25); background: rgba(12, 13, 16, .72); backdrop-filter: blur(8px); -webkit-backdrop-filter: blur(8px); }
.scene-switch button { display: flex; align-items: center; gap: 6px; min-height: 32px; padding: 0 11px; border: 0; background: transparent; color: #d9d6d1; font-size: 10px; font-weight: 900; letter-spacing: .08em; white-space: nowrap; }
.scene-switch .icon { width: 13px; height: 13px; }
.scene-switch button[aria-pressed='true'] { background: var(--orange); color: #15171a; }
.stage-hint { position: absolute; left: 50%; bottom: 16px; transform: translateX(-50%); padding: 8px 13px; background: rgba(14, 16, 20, .7); color: #f5efe9; font-size: 10px; font-weight: 900; letter-spacing: .1em; white-space: nowrap; pointer-events: none; transition: opacity 300ms; }
.hint-touch { display: none; }
@media (hover: none) { .hint-fine { display: none; } .hint-touch { display: inline; } }
.stage.lighting .stage-hint, .stage[data-state='zoom'] .stage-hint { opacity: 0; }

/* A compact index next to the whole scene keeps the image as the main attraction. */
.guide { min-width: 0; border: 1px solid var(--line); background: var(--card); }
.guide-empty { display: flex; flex-direction: column; height: 100%; padding: 24px; }
.guide-index { color: var(--orange-ink); font-size: 10px; font-weight: 900; letter-spacing: .16em; }
.guide-empty h2 { margin: 10px 0 7px; font: 700 clamp(22px, 2vw, 29px)/1.12 Be Vietnam Pro, sans-serif; letter-spacing: -.045em; text-wrap: balance; }
.guide-empty p { margin: 0; color: var(--muted); font-size: 13.5px; line-height: 1.55; }
.spot-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 6px; margin-top: auto; padding-top: 20px; }
.spot-list button { display: flex; align-items: center; gap: 7px; min-height: 42px; padding: 6px 9px; border: 1px solid #d3ccc3; background: #fff; font-size: 10.5px; font-weight: 800; text-align: left; line-height: 1.2; }
.spot-list button b { color: var(--orange-ink); font-size: 9px; }
.spot-list button:hover, .spot-list button:focus-visible { border-color: var(--orange); background: var(--tint); }

/* Focus view: one screen. Close-up photo on the left, angles and knowledge tabs on the right; the page underneath is locked. */
html.focus-open { overflow: hidden; }
.focus { position: fixed; inset: 0; z-index: 40; display: grid; grid-template-columns: minmax(0, 1fr) minmax(340px, 400px); gap: 18px; padding: 18px; background: rgba(244, 241, 236, .97); opacity: 0; transition: opacity 250ms ease; }
.focus.in { opacity: 1; }
.focus-photo { position: relative; align-self: center; justify-self: center; width: min(100%, calc((100vh - 36px) * 1.5)); aspect-ratio: 3 / 2; overflow: hidden; border: 1px solid #cfc8bf; background: #0b0c0f; }
.angle-count { position: absolute; left: 14px; bottom: 14px; padding: 7px 11px; background: rgba(12, 13, 16, .72); color: #f5efe9; font-size: 10px; font-weight: 900; letter-spacing: .12em; }
.focus-panel { display: flex; flex-direction: column; max-height: calc(100vh - 36px); overflow-y: auto; padding: 20px 22px; border: 1px solid var(--line); background: var(--card); }
.focus-top { display: flex; align-items: center; justify-content: space-between; gap: 10px; }
.close { width: 38px; height: 38px; border: 1px solid #c9c2b9; background: #fff; font-size: 22px; line-height: 1; }
.close:hover { border-color: var(--orange); color: var(--orange-ink); }
.kicker { margin: 12px 0 2px; color: var(--orange-ink); font-size: 11px; font-weight: 900; letter-spacing: .15em; }
.focus-panel h2 { margin-bottom: 14px; font: 700 clamp(24px, 2.1vw, 32px)/1.08 Be Vietnam Pro, sans-serif; letter-spacing: -.05em; }
.list-label { display: flex; justify-content: space-between; gap: 8px; margin-bottom: 8px; font-size: 10px; font-weight: 900; letter-spacing: .13em; }
.list-label span { color: #8a857f; font-size: 9px; letter-spacing: .08em; }
.points { display: grid; gap: 5px; margin: 0 0 16px; padding: 0; list-style: none; }
.point { display: grid; grid-template-columns: 24px 1fr; gap: 2px 8px; width: 100%; padding: 9px 11px; border: 1px solid #d3ccc3; background: #fff; text-align: left; transition: border-color 200ms, background 200ms; }
.point b { grid-row: span 2; color: var(--orange-ink); font-size: 11px; font-weight: 900; }
.point strong { font-size: 13px; font-weight: 800; }
.point small { display: none; color: var(--muted); font-size: 12.5px; line-height: 1.5; }
.point.active small { display: block; }
/* The PC interior has 7 parts: two columns keep the list short; the active part spans the row to show its sentence. */
.points.compact { grid-template-columns: 1fr 1fr; }
.points.compact li:has(.active) { grid-column: 1 / -1; }
.point:hover, .point.active { border-color: var(--orange); background: var(--tint); }

.lesson { padding-top: 14px; border-top: 2px solid var(--ink); }
.lesson-name { margin-bottom: 10px; }
.lesson-name b { font: 700 19px/1.2 Be Vietnam Pro, sans-serif; letter-spacing: -.03em; }
.lesson-name span { color: var(--orange-ink); font-weight: 800; font-size: 13px; }
.tabs { display: flex; gap: 4px; margin-bottom: 14px; border-bottom: 1px solid var(--line); }
.tabs button { flex: 1; min-height: 36px; padding: 0 6px; border: 0; border-bottom: 2px solid transparent; margin-bottom: -1px; background: none; color: var(--soft); font-size: 10px; font-weight: 900; letter-spacing: .09em; }
.tabs button[aria-selected='true'] { border-bottom-color: var(--orange); color: var(--ink); }
.tabs button:hover { color: var(--ink); }
.lesson h3 { margin: 0 0 7px; color: var(--orange-ink); font-size: 10px; font-weight: 900; letter-spacing: .15em; }
.tab-panel h3 + p, .tab-panel h3 + ul { margin-bottom: 14px; }
.lesson p { margin-top: 0; color: var(--muted); font-size: 13.5px; line-height: 1.58; }
.lesson p.lead { color: var(--ink); font-size: 15px; font-weight: 600; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; padding: 0; list-style: none; }
.chips li { padding: 6px 10px; border: 1px solid #cfc8bf; background: #fff; font-size: 12px; line-height: 1.3; }
.lesson-tip { padding: 12px 14px; border-left: 3px solid var(--orange); background: #f6e9df; }
.lesson-tip p { margin: 0; }
.source-link { display: flex; justify-content: space-between; align-items: center; gap: 8px; margin-top: 14px; padding-bottom: 8px; border-bottom: 1px solid #d7b8a5; font-size: 10px; font-weight: 900; letter-spacing: .11em; }
.source-link span { color: var(--orange); font-size: 17px; }
.source-link:hover { color: var(--orange-ink); }
.focus-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 6px; margin-top: auto; padding-top: 16px; }
.focus-nav button { min-height: 42px; border: 1px solid #c9c2b9; background: #fff; font-size: 10px; font-weight: 900; letter-spacing: .1em; }
.focus-nav #next { border-color: var(--ink); background: var(--ink); color: #fff; }
.focus-nav #next span { color: var(--orange); }
.focus-nav button:hover { border-color: var(--orange); }

.footnote { display: flex; justify-content: space-between; align-items: flex-start; gap: 30px; margin-top: 22px; padding-top: 22px; border-top: 1px solid var(--line); }
.footnote p { max-width: 760px; margin: 0; color: var(--muted); font-size: 12px; line-height: 1.6; }
.footnote a { display: flex; gap: 14px; padding-bottom: 7px; border-bottom: 1px solid var(--orange); font-size: 10px; font-weight: 900; letter-spacing: .09em; white-space: nowrap; }
.footnote a span { color: var(--orange); }

@media (max-width: 1100px) {
  .explore { display: block; }
  .guide { border-top: 0; }
  .guide-empty { display: grid; grid-template-columns: minmax(220px, .8fr) 1.6fr; gap: 24px; align-items: center; padding: 22px 24px; }
  .spot-list { margin-top: 0; padding-top: 0; grid-template-columns: repeat(auto-fill, minmax(128px, 1fr)); }
}
@media (max-width: 800px) {
  .intro { display: block; padding: 34px 0 22px; }
  .intro-copy { margin-top: 16px; }
  .explore { max-width: none; }
  /* On phones the photo stays pinned on top while the explanation scrolls below it. */
  .stage { position: sticky; top: 0; z-index: 5; }
  .guide-empty { display: block; }
  .guide-empty > div:first-child { margin-bottom: 16px; }
  .spot-list { grid-template-columns: 1fr 1fr; }
  /* Phones: the focus view scrolls as one column, the close-up stays pinned on top. */
  .focus { display: block; overflow-y: auto; padding: 0; background: var(--paper); }
  .focus-photo { position: sticky; top: 0; z-index: 2; width: 100%; border-width: 0 0 1px; }
  .focus-panel { max-height: none; overflow: visible; border: 0; }
}
@media (max-width: 560px) {
  .site-header { min-height: 64px; padding: 0 17px; }
  .brand img { width: 148px; }
  .header-kicker { font-size: 8px; }
  .section { padding: 0 0 30px; }
  .intro { padding: 28px 17px 20px; }
  h1 { font-size: clamp(22px, 6.2vw, 30px); }
  .stage { border-left: 0; border-right: 0; }
  .scene-switch { top: 8px; right: 8px; }
  .scene-switch button { min-height: 28px; padding: 0 8px; font-size: 8.5px; }
  .stage-hint { bottom: 10px; padding: 6px 10px; font-size: 8px; }
  .angle-count { left: 8px; bottom: 8px; font-size: 8.5px; }
  .spot-name { font-size: 8.5px; padding: 4px 7px; }
  .guide { border-left: 0; border-right: 0; }
  .guide-empty, .focus-panel { padding: 18px 17px; }
  .footnote { display: block; padding: 18px 17px 0; }
  .footnote a { width: fit-content; margin-top: 14px; }
}
@media (prefers-reduced-motion: reduce) {
  :root { --zoom: 1ms; --fade: 1ms; }
  .stage, .stage.sweeping { --light-fade: 1ms; }
  .dim { transition: opacity 1ms; }
  .spot-name, .spotlight.on .spot-name { transition: none; }
  .shot { transition: opacity 1ms; transform: none; }
}