@font-face {
  font-family: Inter;
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url("assets/fonts/inter.woff2") format("woff2");
}

@font-face {
  font-family: "Noto Sans SC";
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url("assets/fonts/noto-sans-sc.woff2") format("woff2");
}

:root {
  --paper: #f7f4ef;
  --ink: #171716;
  --fine: #5c5956;
  --button: #1a1a1a;
  --button-text: #f4f1ec;
  --line: #8a8682;
  --nav-x: 22px;
  --ring: min(86vw, 340px);
  color-scheme: light;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--paper);
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  background: var(--paper);
  color: var(--ink);
  font-family: Inter, "Noto Sans SC", sans-serif;
  font-weight: 450;
  font-synthesis: none;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  overflow-x: clip;
}

img {
  max-width: 100%;
  height: auto;
}

a {
  color: inherit;
  text-decoration: none;
}

:focus {
  outline: none;
}

:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 3px;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: max(28px, env(safe-area-inset-top)) max(var(--nav-x), env(safe-area-inset-right)) 0
    max(var(--nav-x), env(safe-area-inset-left));
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  font-size: 20px;
  font-weight: 500;
  letter-spacing: -0.03em;
  line-height: 1;
}

.brand img {
  width: 26px;
  height: 26px;
  display: block;
  border-radius: 6px;
}

.nav nav {
  display: flex;
  align-items: center;
  gap: 0;
  font-size: 15px;
  font-weight: 500;
  letter-spacing: -0.01em;
}

.nav-github {
  display: none;
}

main {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 46px max(16px, env(safe-area-inset-right)) max(22px, env(safe-area-inset-bottom))
    max(16px, env(safe-area-inset-left));
}

.eyebrow {
  margin: 0;
  font-family: Inter, sans-serif;
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.2em;
  text-indent: 0.2em;
  line-height: 1.2;
}

h1 {
  margin: 12px 0 0;
  max-width: 100%;
  font-family: "Noto Sans SC", sans-serif;
  font-weight: 700;
  font-size: 29px;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h1 .opt {
  font-family: Inter, sans-serif;
  font-weight: 500;
  letter-spacing: -0.02em;
}

.lede {
  margin: 10px 0 0;
  max-width: 36em;
  font-size: 13.5px;
  font-weight: 450;
  line-height: 1.45;
  letter-spacing: 0.005em;
}

.hero {
  /* 8 equal slots on the mid-band of a 400×400 ring:
     outer r=172, inner r=84, mid r=128. Icons and plus
     wells share that circle, 45° apart, WeChat at 0°. */
  --slot-cx: 50%;
  --slot-cy: 50%;
  --slot-r: 0.32;
  --slot-icon: 0.158;
  position: relative;
  width: var(--ring);
  aspect-ratio: 1;
  margin: 22px 0 22px;
  overflow: visible;
}

.ring-art {
  display: block;
  width: 100%;
  height: auto;
  overflow: visible;
  filter:
    drop-shadow(0 14px 24px rgba(48, 42, 36, 0.10))
    drop-shadow(0 3px 6px rgba(48, 42, 36, 0.05));
}

.ring-label {
  position: absolute;
  left: 50%;
  top: 50%;
  margin: 0;
  transform: translate(-50%, -50%);
  font-family: "Noto Sans SC", sans-serif;
  font-size: calc(var(--ring) * 0.042);
  font-weight: 500;
  letter-spacing: 0.12em;
  text-indent: 0.12em;
  color: #4a4744;
  line-height: 1;
  pointer-events: none;
}

.slots {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  pointer-events: none;
}

.slot {
  position: absolute;
  left: var(--slot-cx);
  top: var(--slot-cy);
  width: calc(var(--ring) * var(--slot-icon));
  height: calc(var(--ring) * var(--slot-icon));
  transform:
    translate(-50%, -50%)
    rotate(var(--a))
    translateY(calc(var(--ring) * var(--slot-r) * -1))
    rotate(calc(-1 * var(--a)));
}

.slot img {
  display: block;
  width: 100%;
  height: 100%;
  filter: drop-shadow(0 1px 1.2px rgba(23, 23, 22, 0.12));
}

.downloads {
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 8px;
  scroll-margin-top: 24px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 44px;
  padding: 0 16px;
  border-radius: 999px;
  border: 1px solid transparent;
  font-size: 14.5px;
  font-weight: 500;
  letter-spacing: 0.005em;
  line-height: 1;
  white-space: nowrap;
  transition: background-color 160ms ease, border-color 160ms ease, color 160ms ease;
}

.btn-primary {
  background: var(--button);
  color: var(--button-text);
}

.btn-secondary {
  background: transparent;
  color: var(--ink);
  border-color: var(--line);
}

.fine {
  margin: 14px 0 0;
  font-size: 11.5px;
  font-weight: 450;
  line-height: 1.45;
  letter-spacing: 0.005em;
  color: var(--fine);
  white-space: nowrap;
}

@media (hover: hover) and (pointer: fine) {
  .brand:hover,
  .nav a:hover {
    opacity: 0.55;
  }

  .btn-primary:hover {
    background: #000;
  }

  .btn-secondary:hover {
    background: rgba(23, 23, 22, 0.04);
    border-color: #1c1c1c;
  }
}

@media (min-width: 760px) {
  :root {
    --nav-x: 42px;
    --ring: 430px;
  }

  .nav {
    padding-top: 16px;
  }

  .nav-github {
    display: inline;
    margin-left: 36px;
  }

  .brand {
    font-size: 21px;
  }

  .brand img {
    width: 24px;
    height: 24px;
    border-radius: 5.5px;
  }

  .nav nav {
    font-size: 15px;
  }

  main {
    padding-top: 8px;
    padding-bottom: 22px;
  }

  .eyebrow {
    margin-top: 4px;
    font-size: 12px;
    font-weight: 500;
    letter-spacing: 0.135em;
    text-indent: 0.135em;
  }

  h1 {
    margin-top: 14px;
    font-size: 43px;
    font-weight: 640;
    letter-spacing: -0.028em;
  }

  h1 .opt {
    font-weight: 500;
    letter-spacing: -0.02em;
  }

  .lede {
    margin-top: 12px;
    font-size: 16.5px;
    font-weight: 500;
    letter-spacing: 0.012em;
  }

  .hero {
    margin-top: 18px;
    margin-bottom: 18px;
  }

  .downloads {
    gap: 20px;
    margin-top: 0;
  }

  .btn {
    height: 46px;
    padding: 0 22px;
    font-size: 15px;
    font-weight: 500;
  }

  .btn-primary {
    min-width: 228px;
  }

  .btn-secondary {
    min-width: 206px;
  }

  .fine {
    margin-top: 16px;
    font-size: 13px;
    letter-spacing: 0.008em;
    color: #4a4744;
  }
}

@media (prefers-reduced-motion: reduce) {
  .btn,
  .brand,
  .nav a {
    transition: none;
  }
}

/* motion */

.hero-stage {
  perspective: 1100px;
  perspective-origin: 50% 45%;
}

.hero-tilt {
  transform-style: preserve-3d;
  will-change: transform;
}

.nav {
  animation: fade-in 0.55s ease both;
}

.eyebrow {
  animation: fade-up 0.65s cubic-bezier(0.22, 1, 0.36, 1) 0.05s both;
}

h1 {
  animation: fade-up 0.7s cubic-bezier(0.22, 1, 0.36, 1) 0.12s both;
}

.lede {
  animation: fade-up 0.7s cubic-bezier(0.22, 1, 0.36, 1) 0.2s both;
}

.hero {
  animation: ring-in 0.9s cubic-bezier(0.22, 1, 0.36, 1) 0.18s both;
}

.slot-inner {
  display: block;
  width: 100%;
  height: 100%;
  transform-origin: 50% 50%;
  animation: slot-in 0.52s cubic-bezier(0.22, 1, 0.36, 1) backwards;
  animation-delay: calc(0.46s + var(--i, 0) * 0.07s);
}

.slot img {
  transition: filter 0.35s ease;
}

.downloads {
  animation: fade-up 0.7s cubic-bezier(0.22, 1, 0.36, 1) 0.88s both;
}

.fine {
  animation: fade-up 0.65s ease 1s both;
}

.r-cyan-wash {
  animation: cyan-breath 4.2s ease-in-out 1.2s infinite;
}

.btn {
  transition:
    background-color 160ms ease,
    border-color 160ms ease,
    color 160ms ease,
    transform 160ms ease,
    box-shadow 160ms ease;
}

.btn:active {
  transform: scale(0.97);
}

@keyframes fade-in {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes fade-up {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}

@keyframes ring-in {
  from {
    opacity: 0;
    transform: scale(0.96);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes slot-in {
  from {
    opacity: 0;
    transform: scale(0.72);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes cyan-breath {
  0%, 100% { opacity: 0.7; }
  50% { opacity: 1; }
}

@media (hover: hover) and (pointer: fine) {
  .slots {
    pointer-events: none;
  }

  .slot {
    pointer-events: auto;
  }

  .slot-inner {
    transition: transform 0.4s cubic-bezier(0.22, 1, 0.36, 1);
  }

  .slot:hover .slot-inner {
    transform: translateY(-3px) scale(1.08);
  }

  .slot:hover img {
    filter: drop-shadow(0 4px 8px rgba(23, 23, 22, 0.2));
  }

  .btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 16px rgba(23, 23, 22, 0.18);
  }

  .btn-secondary:hover {
    transform: translateY(-1px);
  }

  .btn-primary:active,
  .btn-secondary:active {
    transform: scale(0.97);
    box-shadow: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  .nav,
  .eyebrow,
  h1,
  .lede,
  .hero,
  .slot-inner,
  .downloads,
  .fine,
  .r-cyan-wash,
  .btn,
  .brand,
  .nav a {
    animation: none !important;
    transition: none !important;
  }

  .btn:active,
  .btn-primary:hover,
  .btn-secondary:hover,
  .btn-primary:active,
  .btn-secondary:active,
  .slot:hover .slot-inner {
    transform: none;
  }
}