/* DeltaCE's page: a dark graph-paper hero, a scrolling tour with the calculator held in place,
   the installer, the versions. The app's teal (src/ui_gfx.c): #007a7a on Paper, #34ccbc on Night. */
:root {
  --night: #0b1416;
  --night-2: #10201f;
  --night-ink: #e9f3f2;
  --night-sub: #9db3b5;
  --night-line: rgba(233, 243, 242, .1);
  --bg: #f4f7f6;
  --card: #ffffff;
  --ink: #0f1719;
  --sub: #56646b;
  --line: #dce4e3;
  --acc: #007a7a;
  --acc-bright: #34ccbc;
  --acc-soft: #daf0ed;
  --on-acc: #ffffff;
  --green: #24894a;
  --red: #c4403c;
  --radius: 18px;
  --shadow: 0 1px 2px rgba(15, 23, 25, .05), 0 12px 32px rgba(15, 23, 25, .08);
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a1012;
    --card: #111a1c;
    --ink: #e8eeee;
    --sub: #94a4a8;
    --line: #22302f;
    --acc: #34ccbc;
    --acc-soft: #0f2b2a;
    --on-acc: #061012;
    --green: #56c882;
    --red: #ff7066;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 12px 32px rgba(0, 0, 0, .35);
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 17px/1.6 "Manrope", system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
a { color: var(--acc); text-underline-offset: 3px; }
img { max-width: 100%; height: auto; }
h1, h2, h3 { margin: 0; line-height: 1.12; }
h2 { font-size: clamp(1.8rem, 4.2vw, 2.9rem); font-weight: 800; letter-spacing: -.02em; }
h3 { font-size: 1.25rem; font-weight: 800; letter-spacing: -.01em; }
p { margin: 0 0 .9rem; }
.m { font-family: "STIX Two Text", Georgia, serif; font-style: italic; }
code { font-size: .92em; }
kbd {
  display: inline-block;
  min-width: 1.6em;
  padding: 0 .42em;
  border: 1px solid var(--line);
  border-bottom-width: 2px;
  border-radius: 6px;
  background: var(--card);
  color: var(--ink);
  font: 700 .8em/1.65 "Manrope", system-ui, sans-serif;
  text-align: center;
  white-space: nowrap;
}
.eyebrow {
  margin: 0 0 .9rem;
  color: var(--acc);
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .16em;
  text-transform: uppercase;
}
.fine { font-size: .86rem; color: var(--sub); }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  padding: 0 1.3rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  font: 800 .98rem "Manrope", system-ui, sans-serif;
  text-decoration: none;
  cursor: pointer;
  transition: transform .15s, filter .15s, border-color .15s;
}
.btn:hover { transform: translateY(-1px); border-color: var(--acc); }
.btn.primary { background: var(--acc); border-color: var(--acc); color: var(--on-acc); }
.btn.primary:hover { filter: brightness(1.08); }
.btn:disabled { opacity: .45; cursor: not-allowed; transform: none; filter: none; }
.btn.attn { background: var(--green); border-color: var(--green); color: #fff; animation: attn 1.6s ease-in-out infinite; }
@keyframes attn { 0%, 100% { box-shadow: 0 0 0 0 rgba(36, 137, 74, .55); } 50% { box-shadow: 0 0 0 9px rgba(36, 137, 74, 0); } }

/* ---------------------------------------------------------------- the floating nav */
.pill {
  position: fixed;
  top: 14px;
  left: 50%;
  z-index: 20;
  transform: translateX(-50%);
  display: flex;
  align-items: center;
  gap: .2rem;
  padding: .3rem .4rem;
  border-radius: 999px;
  background: rgba(11, 20, 22, .72);
  border: 1px solid rgba(233, 243, 242, .12);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 8px 28px rgba(0, 0, 0, .25);
}
.pill a {
  color: var(--night-sub);
  text-decoration: none;
  font-size: .9rem;
  font-weight: 700;
  padding: .38rem .8rem;
  border-radius: 999px;
  white-space: nowrap;
}
.pill a:hover { color: var(--night-ink); background: rgba(233, 243, 242, .08); }
.pill .pill-mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  padding: 0;
  background: var(--acc-bright);
  color: var(--night);
  font-weight: 800;
}
.pill .pill-mark:hover { background: var(--acc-bright); color: var(--night); filter: brightness(1.1); }

/* ---------------------------------------------------------------- the hero */
.hero {
  position: relative;
  overflow: hidden;
  min-height: min(100svh, 980px);
  display: flex;
  align-items: center;
  background: radial-gradient(1200px 600px at 75% 40%, #12302d 0%, var(--night) 60%);
  color: var(--night-ink);
  padding: 104px 20px 80px;
}
.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(52, 204, 188, .07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(52, 204, 188, .07) 1px, transparent 1px);
  background-size: 44px 44px;
  mask-image: radial-gradient(ellipse at 60% 45%, #000 30%, transparent 78%);
  -webkit-mask-image: radial-gradient(ellipse at 60% 45%, #000 30%, transparent 78%);
}
.hero-in {
  position: relative;
  width: 100%;
  max-width: 1180px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1.08fr;
  gap: 3rem;
  align-items: center;
}
.hero .eyebrow { color: var(--acc-bright); }
.mark {
  font-family: "STIX Two Text", Georgia, serif;
  font-style: italic;
  font-weight: 500;
  font-size: clamp(4rem, 10vw, 7.4rem);
  letter-spacing: -.01em;
  line-height: 1;
  margin: 0 0 1.1rem;
}
.mark .ce { color: var(--acc-bright); }
.tagline { font-size: clamp(1.25rem, 2.4vw, 1.65rem); font-weight: 800; letter-spacing: -.01em; line-height: 1.3; margin-bottom: 1rem; }
.intro { color: var(--night-sub); max-width: 34rem; }
.cta { display: flex; flex-wrap: wrap; gap: .7rem; margin: 1.6rem 0 1.1rem; }
.hero .btn.primary { background: var(--acc-bright); border-color: var(--acc-bright); color: var(--night); }
.btn.ghost { background: transparent; color: var(--night-ink); border-color: rgba(233, 243, 242, .25); }
.btn.ghost:hover { border-color: var(--acc-bright); }
.hero-fine { font-size: .88rem; color: var(--night-sub); }
.hero-fine a { color: var(--acc-bright); }
.ver-tag { padding: .05rem .5rem; border-radius: 999px; background: rgba(52, 204, 188, .15); color: var(--acc-bright); font-weight: 800; text-decoration: none; }
.hero-fine a.ver-tag:hover { background: rgba(52, 204, 188, .28); }
.btn.gh { gap: .5rem; }

/* the secant turning into the tangent (site.js draws and animates it) */
.secant {
  margin: 0;
  border-radius: 24px;
  border: 1px solid var(--night-line);
  background: linear-gradient(160deg, rgba(16, 32, 31, .85), rgba(11, 20, 22, .6));
  box-shadow: 0 30px 80px rgba(0, 0, 0, .35), inset 0 1px 0 rgba(233, 243, 242, .05);
  padding: 10px 10px 0;
}
.secant svg { display: block; width: 100%; height: auto; }
.axes line { stroke: rgba(233, 243, 242, .2); stroke-width: 1.5; }
.curve { fill: none; stroke: url(#curve-ink); stroke-width: 4.5; stroke-linecap: round; }
.sec { opacity: 0; }
.sec-line { stroke: #e9f3f2; stroke-width: 2.2; opacity: .9; transition: stroke .3s; }
.secant.locked .sec-line { stroke: var(--acc-bright); filter: url(#glow); }
.leg { stroke: rgba(233, 243, 242, .7); stroke-width: 1.8; stroke-dasharray: 6 5; }
.leg-lab { fill: #d5e8e6; font: italic 500 24px "STIX Two Text", Georgia, serif; }
.dot.p { fill: #fff; stroke: var(--acc-bright); stroke-width: 3; }
.dot.q { fill: var(--night); stroke: #f4fbfa; stroke-width: 3; }
.pulse { fill: none; stroke: var(--acc-bright); stroke-width: 2; opacity: 0; }
.readout {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: .4rem 1rem;
  padding: .85rem 1.1rem 1rem;
  border-top: 1px solid var(--night-line);
  font: 500 1.2rem/1.3 "STIX Two Text", Georgia, serif;
  color: var(--night-sub);
}
.readout b { font: 800 1.05rem "Manrope", system-ui, sans-serif; font-variant-numeric: tabular-nums; color: var(--night-ink); }
.ro-lim { opacity: .35; transition: opacity .4s, color .4s; }
.secant.locked .ro-lim { opacity: 1; color: var(--acc-bright); }

.scroll-cue {
  position: absolute;
  left: 50%;
  bottom: 22px;
  width: 24px;
  height: 38px;
  margin-left: -12px;
  border: 2px solid rgba(233, 243, 242, .3);
  border-radius: 14px;
}
.scroll-cue span {
  position: absolute;
  left: 50%;
  top: 7px;
  width: 4px;
  height: 8px;
  margin-left: -2px;
  border-radius: 2px;
  background: var(--acc-bright);
  animation: cue 1.8s ease-in-out infinite;
}
@keyframes cue { 0% { transform: translateY(0); opacity: 1; } 70% { transform: translateY(12px); opacity: 0; } 100% { opacity: 0; } }

/* ---------------------------------------------------------------- sections */
section { padding: 6.5rem 20px 0; scroll-margin-top: 70px; }
.sec-head { max-width: 1180px; margin: 0 auto 2.6rem; }
.sec-head h2 { max-width: 18em; }
.sec-lead { margin-top: 1rem; color: var(--sub); font-size: 1.1rem; max-width: 40rem; }

/* the tour: chapters on the left, the calculator held in place on the right */
.tour {
  max-width: 1180px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
}
.chapter {
  min-height: 74vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  max-width: 30rem;
  opacity: .32;
  transition: opacity .45s;
}
.chapter.on { opacity: 1; }
.ch-num {
  display: block;
  font: italic 500 3.2rem/1 "STIX Two Text", Georgia, serif;
  color: var(--acc);
  margin-bottom: .8rem;
}
.chapter h3 { font-size: clamp(1.5rem, 2.6vw, 2rem); margin-bottom: .9rem; }
.chapter p { color: var(--sub); font-size: 1.05rem; }
.ch-img { display: none; }

.stage {
  position: sticky;
  top: 0;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.6rem;
}
.device {
  width: min(400px, 100%);
  padding: 22px 22px 26px;
  border-radius: 34px 34px 48px 48px;
  background: linear-gradient(170deg, #1f2a2d, #0f1517 70%);
  box-shadow: 0 40px 90px rgba(11, 20, 22, .35), inset 0 1px 0 rgba(255, 255, 255, .08), inset 0 -3px 0 rgba(0, 0, 0, .4);
}
.screen {
  position: relative;
  aspect-ratio: 4 / 3;
  border-radius: 10px;
  overflow: hidden;
  border: 6px solid #070b0c;
  background: #f7f8fa;
}
.shot { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; image-rendering: auto; }
.keys { display: grid; gap: 10px; margin-top: 22px; }
.keys span { display: grid; grid-template-columns: repeat(5, 1fr); gap: 10px; }
.keys i { display: block; height: 18px; border-radius: 7px; background: #2a3538; box-shadow: inset 0 -2px 0 rgba(0, 0, 0, .35); }
.keys .frow i { height: 12px; background: #2f6763; }
.keys .krow:nth-child(2) { grid-template-columns: repeat(3, 1fr) 1.6fr; }
.keys .pad { height: 18px; border-radius: 999px; background: #354246; }
.rail { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.rail li { width: 6px; height: 6px; border-radius: 99px; background: var(--line); transition: height .35s, background .35s; }
.rail li.on { height: 26px; background: var(--acc); }

/* everything else */
.also { text-align: left; }
.tags {
  max-width: 1180px;
  margin: 0 auto;
  padding: 0;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: .6rem;
}
.tags li {
  padding: .5rem 1rem;
  border-radius: 999px;
  background: var(--card);
  border: 1px solid var(--line);
  font-weight: 700;
  font-size: .95rem;
}
.tags li:nth-child(4n + 1) { border-color: color-mix(in srgb, var(--acc) 45%, var(--line)); }

/* install */
.install {
  max-width: 1180px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: .9fr 1.1fr;
  gap: 3.5rem;
  align-items: start;
}
.install-copy { position: sticky; top: 90px; }
.install-copy h2 { margin-bottom: 1.1rem; }
.install-copy > p { color: var(--sub); font-size: 1.05rem; }
.needs { margin: 1.2rem 0; padding: 0; list-style: none; display: grid; gap: .6rem; }
.needs li { position: relative; padding-left: 1.6rem; color: var(--sub); }
.needs li::before { content: "Δ"; position: absolute; left: 0; color: var(--acc); font-weight: 800; }
.needs strong { color: var(--ink); }
.installer {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: .6rem 1.6rem 1.2rem;
}
.notice { margin: 1rem 0 .4rem; padding: .85rem 1rem; border-radius: 12px; background: var(--acc-soft); }
.steps { list-style: none; margin: 0; padding: 0; }
.step { border-bottom: 1px solid var(--line); padding: 1.2rem 0; }
.step-head { display: flex; align-items: center; gap: .85rem; }
.num {
  flex: none;
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  border-radius: 12px;
  border: 2px solid var(--line);
  font-weight: 800;
  color: var(--sub);
}
.step.active .num { border-color: var(--acc); background: var(--acc); color: var(--on-acc); }
.step.done .num { background: var(--green); border-color: var(--green); color: #fff; }
.step-body { padding: .7rem 0 0 calc(34px + .85rem); }
.step-body > p { color: var(--sub); }
.step .gif { display: none; }
.step.active .gif { display: block; }
.gif { width: 100%; max-width: 380px; margin: .9rem 0 .4rem; border-radius: 12px; border: 1px solid var(--line); }
.confirm { display: flex; align-items: center; gap: .55rem; margin: .1rem 0 .9rem; font-weight: 700; cursor: pointer; }
.confirm input { width: 18px; height: 18px; accent-color: var(--red); }
.status { margin-top: .75rem; font-size: .95rem; }
.status:empty { display: none; }
.status .ok { color: var(--green); font-weight: 800; }
.status .bad { color: var(--red); font-weight: 800; }
.status ul { margin: .3rem 0 0; padding-left: 1.2rem; }
.progress { margin-top: .9rem; max-width: 520px; }
.bar { height: 10px; border-radius: 99px; background: var(--acc-soft); overflow: hidden; }
.bar span { display: block; height: 100%; width: 0; background: var(--acc); transition: width .2s; }
details.more { border-top: 1px solid var(--line); padding: .9rem 0 .2rem; }
details.more summary { cursor: pointer; font-weight: 800; }
details.more ol, details.more ul { margin: .7rem 0 .3rem; padding-left: 1.3rem; color: var(--sub); }
details.more li { margin-bottom: .45rem; }

/* versions */
.versions-sec { padding-bottom: 6rem; }
.timeline {
  position: relative;
  max-width: 1180px;
  margin: 0 auto;
  padding: 0 0 0 2.2rem;
  list-style: none;
}
.timeline::before { content: ""; position: absolute; left: 8px; top: 10px; bottom: 10px; width: 2px; background: var(--line); }
.timeline li { position: relative; display: grid; grid-template-columns: 4.2rem 1fr; gap: 1rem; padding: .7rem 0; }
.timeline li::before {
  content: "";
  position: absolute;
  left: calc(-2.2rem + 3px);
  top: 1.15rem;
  width: 12px;
  height: 12px;
  border-radius: 99px;
  background: var(--bg);
  border: 2px solid var(--acc);
}
.timeline li.now::before { background: var(--acc); box-shadow: 0 0 0 6px var(--acc-soft); }
.timeline b { font: italic 500 1.5rem/1.2 "STIX Two Text", Georgia, serif; color: var(--acc); }
.timeline span { color: var(--sub); padding-top: .25rem; }
.timeline li.now span { color: var(--ink); font-weight: 700; }
.timeline .older { display: none; }
.timeline.all .older { display: grid; }
.versions-sec .btn { margin: 1.4rem 0 0 calc(2.2rem + 4.2rem + 1rem); }
.btn.ghost.dark-ghost { background: transparent; color: var(--ink); border-color: var(--line); }
.btn.ghost.dark-ghost:hover { border-color: var(--acc); }

/* footer */
.foot { background: var(--night); color: var(--night-sub); padding: 3.5rem 20px 3rem; font-size: .86rem; }
.foot-in { max-width: 1180px; margin: 0 auto; }
.foot p { max-width: 62rem; }
.foot a { color: var(--acc-bright); }
.foot-mark { font: italic 500 2rem/1 "STIX Two Text", Georgia, serif; color: var(--night-ink); margin-bottom: 1.2rem; }
.foot-mark span { color: var(--acc-bright); }
.foot-links { font-size: .95rem; font-weight: 700; margin-bottom: 1.4rem; }

/* what site.js reveals as it scrolls into view (visible without scripts or with reduced motion) */
.js [data-reveal] { opacity: 0; }

@media (max-width: 960px) {
  .hero-in { grid-template-columns: 1fr; gap: 2.4rem; }
  .tour { grid-template-columns: 1fr; gap: 0; }
  .stage { display: none; }
  .chapter { min-height: 0; max-width: none; opacity: 1; padding: 2.2rem 0; border-top: 1px solid var(--line); }
  .ch-img { display: block; margin-top: .6rem; border-radius: 14px; border: 1px solid var(--line); box-shadow: var(--shadow); }
  .install { grid-template-columns: 1fr; gap: 2rem; }
  .install-copy { position: static; }
}
@media (max-width: 560px) {
  body { font-size: 16px; }
  .pill { gap: 0; }
  .pill a { padding: .38rem .55rem; font-size: .84rem; }
  .pill a[href="#versions"] { display: none; }
  .hero { padding-top: 92px; }
  section { padding-top: 4.5rem; }
  .installer { padding: .4rem 1.1rem 1rem; }
  .step-body { padding-left: 0; }
  .timeline li { grid-template-columns: 3.4rem 1fr; }
  .versions-sec .btn { margin-left: 2.2rem; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .scroll-cue span, .btn.attn { animation: none; }
  .js [data-reveal] { opacity: 1; }
}