/* ============================================================
   Base — Reset + Typography + Layout primitives
   依賴 tokens.css
   ============================================================ */

/* ---------- Modern reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; }

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-h);
}

body {
  font-family: var(--ff-sans);
  font-size: var(--fs-body);
  line-height: var(--lh-normal);
  color: var(--c-text-2);
  background: var(--c-bg);
  background-image: var(--grad-hero);
  background-attachment: fixed;
  min-height: 100dvh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

img, svg, video, canvas { display: block; max-width: 100%; height: auto; }

button, input, textarea, select { font: inherit; color: inherit; }
button { cursor: pointer; background: none; border: 0; padding: 0; }

a { color: var(--c-accent); text-decoration: none; transition: color var(--dur-fast) var(--ease-out); }
a:hover { color: var(--c-accent-2); }

ul, ol { padding-left: 1.25em; }
li { margin: var(--sp-2) 0; }

::selection { background: var(--c-accent); color: var(--c-bg); }

/* ---------- Typography ---------- */
h1, h2, h3, h4 {
  font-family: var(--ff-display);
  color: var(--c-text);
  line-height: var(--lh-tight);
  font-weight: var(--fw-bold);
  letter-spacing: -0.01em;
}
h1 { font-size: var(--fs-h1); }
h2 { font-size: var(--fs-h2); }
h3 { font-size: var(--fs-h3); }

.t-display {
  font-family: var(--ff-display);
  font-size: var(--fs-display);
  line-height: var(--lh-tight);
  font-weight: var(--fw-black);
  letter-spacing: -0.02em;
  color: var(--c-text);
}

.t-eyebrow {
  display: inline-block;
  font-size: var(--fs-small);
  font-weight: var(--fw-semibold);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--c-accent);
  padding: var(--sp-2) var(--sp-3);
  border: 1px solid var(--c-border);
  border-radius: var(--r-pill);
  background: rgba(34,211,238,0.06);
}

.t-muted { color: var(--c-muted); }
.t-small { font-size: var(--fs-small); }
.t-mono  { font-family: var(--ff-mono); font-feature-settings: "tnum"; }

.t-gradient {
  background: linear-gradient(135deg, var(--c-accent) 0%, #A5F3FC 50%, var(--c-warn) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

/* ---------- Layout primitives ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--sp-5);
}
@media (min-width: 768px) {
  .container { padding-inline: var(--sp-8); }
}

.section {
  padding-block: var(--sp-16);
}
@media (min-width: 768px) {
  .section { padding-block: var(--sp-24); }
}

.section-head {
  text-align: center;
  margin-bottom: var(--sp-12);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-3);
}
.section-head p { max-width: 56ch; color: var(--c-muted); }

/* Skip link for keyboard users */
.skip-link {
  position: absolute;
  top: -100px;
  left: var(--sp-3);
  z-index: 1000;
  padding: var(--sp-2) var(--sp-4);
  background: var(--c-accent);
  color: var(--c-bg);
  border-radius: var(--r-md);
  font-weight: var(--fw-semibold);
}
.skip-link:focus { top: var(--sp-3); }

/* Focus-visible for keyboard navigation */
:focus-visible {
  outline: 2px solid var(--c-accent);
  outline-offset: 3px;
  border-radius: var(--r-sm);
}

/* Reveal-on-scroll utility (used by IntersectionObserver) */
.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity var(--dur-slow) var(--ease-out), transform var(--dur-slow) var(--ease-out);
}
.reveal.is-visible {
  opacity: 1;
  transform: none;
}