.about-page {
  --about-ink: #191f28;
  --about-muted: #4e5968;
  --about-blue: #1557d4;
  --about-rule: #e2e8f0;
  --about-pad: clamp(20px, 5vw, 72px);
  color: var(--about-ink);
  background: #fff;
  word-break: keep-all;
}
.about-page .info-header {
  background: #fff;
  backdrop-filter: none;
  border-color: var(--about-rule);
}
.about-page .info-header nav a { display: inline-flex; align-items: center; min-height: 44px; }
.about-main { max-width: 1440px; margin: 0 auto; }
.launch { padding: clamp(50px, 7.4vw, 104px) var(--about-pad) 0; }
.launch-copy { text-align: center; }
.launch-copy h1 {
  margin: 0;
  font-size: clamp(43px, 6.6vw, 93px);
  line-height: 1.09;
  font-weight: 800;
  letter-spacing: -.085em;
}
.launch-copy p {
  margin: 23px 0 24px;
  color: var(--about-muted);
  font-size: clamp(15px, 1.55vw, 19px);
  line-height: 1.7;
}
.launch-actions { display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 8px 16px; }
.launch-secondary {
  display: inline-flex;
  min-height: 48px;
  align-items: center;
  gap: 9px;
  padding: 0 8px;
  font-size: 14px;
  font-weight: 700;
}
.launch-secondary:hover { color: var(--about-blue); }
.showcase {
  position: relative;
  isolation: isolate;
  height: clamp(320px, 44vw, 506px);
  margin-top: clamp(28px, 4.2vw, 58px);
  overflow: hidden;
  border: 1px solid #deebf9;
  border-radius: 14px;
  background: #eff5fe;
}
.showcase-art { position: absolute; inset: 0; }
.showcase-grid { position: absolute; inset: 0; mask-image: radial-gradient(ellipse at center, #000 5%, transparent 76%); }
.showcase-sign {
  position: absolute;
  color: #688dbd;
  opacity: .6;
  font: italic clamp(27px, 4.8vw, 68px)/1 Georgia, serif;
  user-select: none;
}
.showcase-pi { left: 12%; top: 11%; }
.showcase-sum { right: 12%; top: 12%; }
.showcase-root { left: 16%; bottom: 9%; }
.showcase-layer {
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: var(--width);
  z-index: var(--layer);
  transform: translate(calc(-50% + var(--showcase-progress, 0) * var(--spread)), calc(-50% + var(--showcase-progress, 0) * var(--drift))) rotate(calc(var(--angle) + var(--showcase-progress, 0) * var(--turn)));
}
.showcase-circle { --x: 29%; --y: 52%; --width: min(29%, 305px); --angle: -13deg; --layer: 1; --drift: 32px; --spread: -27px; --turn: -3deg; }
.showcase-graph { --x: 72%; --y: 53%; --width: min(29%, 305px); --angle: 12deg; --layer: 2; --drift: 46px; --spread: 27px; --turn: 3deg; }
.showcase-triangle { --x: 50%; --y: 48%; --width: min(36%, 366px); --angle: -2deg; --layer: 3; --drift: 72px; --spread: 0px; --turn: 2deg; }
.showcase-sheet {
  display: block;
  width: 100%;
  height: auto;
  overflow: hidden;
  border: 1px solid #abc4e1;
  border-radius: 9px;
  box-shadow: 0 15px 32px -13px #2e538464;
}
.sheet-caption { fill: #405a7d; font: 600 13px "Noto Sans KR", sans-serif; }
.sheet-equation { fill: #19417e; font: italic 37px Georgia, serif; }
.sheet-variable { fill: #19417e; font: italic 20px Georgia, serif; }
.sheet-guide, .sheet-axis { fill: none; stroke: #8ea9cb; stroke-width: 1.2; }
.sheet-guide { stroke-dasharray: 4 5; }
.sheet-fill { fill: #bcd5fb; fill-opacity: .56; }
.sheet-line { fill: none; stroke: #2160bd; stroke-width: 2.1; stroke-linejoin: round; }
.sheet-dot { fill: #2160bd; }
.showcase-replay {
  position: absolute;
  z-index: 4;
  right: 18px;
  bottom: 16px;
  display: flex;
  min-height: 44px;
  align-items: center;
  gap: 6px;
  padding: 0 9px;
  border: 0;
  background: #eff5fe;
  color: #254879;
  font-size: 12px;
  font-weight: 700;
}
.showcase-replay[hidden] { display: none; }
.showcase-replay:hover { text-decoration: underline; text-underline-offset: 4px; }
.intro {
  display: grid;
  grid-template-columns: minmax(0, .93fr) minmax(0, 1fr);
  align-items: center;
  gap: clamp(32px, 6vw, 90px);
  padding: clamp(66px, 9vw, 124px) var(--about-pad) clamp(60px, 9vw, 118px);
}
.intro-copy h2 {
  margin: 0;
  font-size: clamp(38px, 4.9vw, 68px);
  line-height: 1.13;
  font-weight: 800;
  letter-spacing: -.087em;
}
.intro-copy p, .notes-intro p, .about-end p {
  margin: 24px 0 28px;
  color: var(--about-muted);
  font-size: clamp(15px, 1.45vw, 18px);
  line-height: 1.8;
}
.about-primary {
  display: inline-flex;
  min-height: 48px;
  align-items: center;
  gap: 20px;
  padding: 0 16px;
  border-radius: 8px;
  background: var(--about-blue);
  color: #fff;
  font-size: 14px;
  font-weight: 700;
  transition: background .2s ease;
}
.about-primary:hover { background: #1044ad; }
.about-page :focus-visible { outline: 2px solid var(--about-blue); outline-offset: 4px; }
.math-board { min-width: 0; margin: 0; scroll-margin-top: 24px; }
.board-heading, .board-caption {
  display: flex;
  min-height: 49px;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.board-heading { border-top: 2px solid var(--about-ink); }
.board-heading h2 { margin: 0; font-size: clamp(13px, 1.4vw, 17px); font-weight: 700; letter-spacing: -.04em; }
#board-equation {
  color: var(--about-blue);
  font-family: Georgia, serif;
  font-size: clamp(23px, 3vw, 38px);
  font-style: italic;
  white-space: nowrap;
}
.plot-window {
  overflow: hidden;
  border: 1px solid #dbe6f2;
  background: #f7fbff;
}
.math-plot { display: block; width: 100%; height: auto; }
.math-plot [hidden], .math-board [hidden] { display: none; }
.construction, .axis { fill: none; stroke: #8195ac; stroke-width: 1.4; }
.construction { stroke-dasharray: 4 5; }
.solid-guide { stroke-dasharray: none; }
.shape-fill { fill: #dceafe; fill-opacity: .88; }
.shape-line { fill: none; stroke: var(--about-blue); stroke-width: 2.5; stroke-linejoin: round; }
.plot-point { fill: #fff; stroke: var(--about-blue); stroke-width: 2.4; }
.plot-label {
  fill: #293f5b;
  font: italic 23px Georgia, serif;
  paint-order: stroke;
  stroke: #f7fbff;
  stroke-linejoin: round;
  stroke-width: 5px;
}
.ink-label { fill: #1049b5; }
.board-caption p {
  min-width: 0;
  margin: 0;
  font-family: Georgia, serif;
  font-size: clamp(16px, 2vw, 24px);
  line-height: 1.25;
  font-variant-numeric: tabular-nums;
}
.board-caption a {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  gap: 4px;
  flex: none;
  color: var(--about-blue);
  font-size: 12px;
  font-weight: 700;
}
.board-caption a:hover { text-decoration: underline; text-underline-offset: 3px; }
.board-controls {
  display: grid;
  min-height: 49px;
  grid-template-columns: 85px minmax(0, 1fr);
  align-items: center;
  gap: 12px;
  border-top: 1px solid var(--about-rule);
}
.board-controls label { font-size: 13px; font-weight: 600; }
.board-controls input {
  width: 100%;
  min-width: 0;
  min-height: 44px;
  margin: 0;
  accent-color: var(--about-blue);
  cursor: pointer;
}
.board-switch {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  min-inline-size: 0;
  padding: 0;
  margin: 0;
  border: 0;
  border-top: 1px solid var(--about-rule);
  border-bottom: 1px solid var(--about-rule);
}
.board-switch label { position: relative; display: block; }
.board-switch input, .about-sr {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}
.board-switch span {
  display: flex;
  min-height: 46px;
  justify-content: center;
  align-items: center;
  padding: 2px 4px;
  border-bottom: 2px solid transparent;
  color: var(--about-muted);
  font-size: 13px;
  text-align: center;
  cursor: pointer;
}
.board-switch label:hover span { background: #f7fbff; }
.board-switch input:checked + span {
  border-bottom-color: var(--about-blue);
  color: var(--about-blue);
  font-weight: 700;
}
.board-switch input:focus-visible + span { outline: 2px solid var(--about-blue); outline-offset: -3px; }
.about-notes {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(24px, 8vw, 120px);
  padding: clamp(56px, 8vw, 112px) var(--about-pad);
  border-top: 1px solid var(--about-rule);
}
.about-notes h2, .about-end h2 {
  margin: 0;
  font-size: clamp(31px, 4.5vw, 61px);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -.075em;
}
.notes-intro p { max-width: 30ch; margin-bottom: 0; }
.notes-list { margin: 0; }
.notes-list div { padding: 20px 0; border-top: 1px solid var(--about-rule); }
.notes-list div:first-child { border-top-color: var(--about-ink); }
.notes-list dt { font-size: 17px; font-weight: 700; letter-spacing: -.04em; }
.notes-list dd { margin: 7px 0 0; color: var(--about-muted); line-height: 1.8; }
.about-end {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  padding: clamp(56px, 8vw, 110px) var(--about-pad);
  background: #f0f5fc;
}
.about-end p { max-width: 31ch; }
.end-mark {
  position: absolute;
  z-index: -1;
  right: clamp(-48px, 4vw, 72px);
  top: 50%;
  transform: translateY(-54%);
  color: #dce8f9;
  font: 400 clamp(210px, 35vw, 440px)/1 Georgia, serif;
  user-select: none;
}
.end-mark > span { display: block; }
@media (max-width: 980px) {
  .intro { grid-template-columns: minmax(0, 1fr); gap: 38px; padding-top: 54px; }
  .intro-copy h2 { font-size: clamp(37px, 6.6vw, 60px); }
  .math-board { width: min(100%, 640px); justify-self: center; }
}
@media (max-width: 600px) {
  .launch { padding-top: 46px; }
  .launch-copy h1 { font-size: clamp(37px, 9.25vw, 55px); }
  .launch-copy p { margin: 17px 0 18px; }
  .launch-actions { column-gap: 8px; }
  .launch-secondary, .launch .about-primary { font-size: 12px; }
  .showcase { height: clamp(268px, 74vw, 375px); border-radius: 9px; }
  .showcase-circle { --x: 21%; --y: 49%; --width: 43%; --drift: 15px; --spread: -8px; }
  .showcase-graph { --x: 79%; --y: 52%; --width: 43%; --drift: 19px; --spread: 8px; }
  .showcase-triangle { --x: 50%; --y: 45%; --width: 57%; --drift: 25px; }
  .showcase-sheet { border-radius: 5px; }
  .showcase-sum { right: 8%; }
  .showcase-root { bottom: 10%; }
  .showcase-replay { right: 8px; bottom: 7px; }
  .intro { gap: 32px; padding-top: 36px; padding-bottom: 52px; }
  .intro-copy h2 { font-size: clamp(33px, 8.3vw, 49px); }
  .intro-copy p { margin: 17px 0 20px; }
  .wide-break { display: none; }
  .board-heading { min-height: 44px; }
  .board-caption p { font-size: 16px; }
  .board-switch span { font-size: 12px; }
  .about-notes { grid-template-columns: minmax(0, 1fr); }
  .end-mark { top: auto; bottom: -64px; transform: none; }
}
@media (prefers-reduced-motion: reduce) {
  .about-page *, .about-page *::before, .about-page *::after { transition: none !important; animation: none !important; }
}