/* Sky Pilot download site. Colours come from the game itself:
   the daytime sky, the Code Lab training field, the HUD slate and the HUD orange. */

@font-face {
  font-family: "Russo One";
  src: url("fonts/RussoOne-Regular.ttf") format("truetype");
  font-display: swap;
}

:root {
  --sky: #d4ecf9;
  --sky-deep: #a9d6f2;
  --field: #2f9a57;
  --field-dark: #237a44;
  --slate: #16222d;
  --slate-soft: #4a5966;
  --orange: #ff8a1f;
  --orange-dark: #e06f05;
  --paper: #f7fbfd;
  --block-blue: #4c97ff;
  --block-orange: #ffab19;
  --block-purple: #9966ff;
  --block-hat: #ffbf00;

  --display: "Russo One", "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  --text: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", "Noto Sans CJK SC", "Segoe UI", system-ui, sans-serif;
  --code: Consolas, "Cascadia Mono", "SF Mono", "Roboto Mono", monospace;

  --step-0: 1.0625rem;
  --step-1: 1.3rem;
  --step-2: clamp(1.6rem, 1.2rem + 1.6vw, 2.3rem);
  --step-3: clamp(2.2rem, 1.3rem + 4vw, 4.4rem);
  --gutter: clamp(16px, 4vw, 56px);
  /* Width of the content column (sections pad around it). */
  --page: 1068px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  margin: 0;
  font-family: var(--text);
  font-size: var(--step-0);
  line-height: 1.7;
  color: var(--slate);
  background: var(--paper);
  -webkit-text-size-adjust: 100%;
}

/* Language: show only the active one. */
html[data-lang="zh"] [lang="en"],
html[data-lang="en"] [lang="zh"] { display: none !important; }
html[data-lang="en"] body { line-height: 1.6; }

img { max-width: 100%; height: auto; display: block; }
a { color: inherit; }
h1, h2, h3 { margin: 0; line-height: 1.2; font-weight: 800; }
h2 { font-size: var(--step-2); }
h3 { font-size: var(--step-1); }
p { margin: 0; }

:focus-visible { outline: 3px solid var(--orange); outline-offset: 3px; border-radius: 6px; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

/* --- Top bar ------------------------------------------------------------- */

.bar {
  position: sticky; top: 0; z-index: 10;
  display: flex; align-items: center; gap: 20px;
  padding: 10px var(--gutter);
  background: rgba(212, 236, 249, 0.86);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; }
.brand img { border-radius: 9px; }
.brand-name { font-family: var(--display); font-size: 1.3rem; letter-spacing: .02em; }
.nav { display: flex; gap: 4px; margin-left: auto; }
.nav a { text-decoration: none; padding: 6px 12px; border-radius: 999px; font-weight: 600; }
.nav a:hover { background: rgba(22, 34, 45, 0.08); }
.nav .nav-download { background: var(--slate); color: #fff; }
.nav .nav-download:hover { background: #24384a; }
.lang-toggle {
  font: inherit; font-weight: 600; cursor: pointer;
  border: 2px solid var(--slate); background: transparent; color: var(--slate);
  border-radius: 999px; padding: 4px 14px;
}
.lang-toggle:hover { background: var(--slate); color: #fff; }

/* --- Real drones used in class (first thing on the page) ----------------------- */

.real { background: var(--slate); color: #fff; padding: 14px var(--gutter); }
.real-inner {
  max-width: calc(var(--page) + 2 * var(--gutter)); margin: 0 auto;
  display: flex; flex-wrap: wrap; align-items: center; gap: 12px 32px;
}
.real-title { font-weight: 800; color: var(--orange); flex: none; }
.real-list { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 12px 32px; flex: 1 1 520px; }
.real-list li { display: flex; align-items: center; gap: 12px; flex: 1 1 240px; max-width: 30em; }
.real-list strong { display: block; font-family: var(--display); font-weight: 400; font-size: 1.15rem; letter-spacing: .02em; line-height: 1.3; }
.real-list li > div > span { display: block; font-size: 0.92rem; color: #c3cfd8; line-height: 1.5; }
.real-list li > div > strong > span { display: inline; }
.real-icon { width: 44px; height: 44px; flex: none; color: #e8ecef; }
.real-note { font-size: 0.92rem; color: #c3cfd8; flex: none; }
html[data-lang="zh"] .real-list strong span[lang="zh"] { font-family: var(--text); font-weight: 800; }

/* --- Hero: the sky --------------------------------------------------------- */

.hero {
  display: grid;
  grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  gap: clamp(24px, 4vw, 64px);
  align-items: center;
  padding: clamp(32px, 6vw, 88px) var(--gutter) clamp(56px, 8vw, 120px);
  background: linear-gradient(180deg, var(--sky) 0%, var(--sky-deep) 100%);
}
.hero h1 {
  font-family: var(--display);
  font-size: var(--step-3);
  font-weight: 400;
  letter-spacing: -0.01em;
  line-height: 1.12;
  text-wrap: balance;
}
html[data-lang="en"] .hero h1 { font-size: clamp(2.2rem, 1.2rem + 3vw, 3.5rem); }
html[data-lang="zh"] .hero h1 {
  font-family: var(--text); font-weight: 900; letter-spacing: 0.02em;
  font-size: clamp(2rem, 1.1rem + 3vw, 3.5rem);
}
.lead { margin-top: 20px; max-width: 34em; font-size: 1.12rem; color: #233645; }
html[data-lang="en"] .lead { max-width: 38em; }
.facts { margin-top: 18px; color: var(--slate-soft); font-size: 0.98rem; }

.get { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 20px; margin-top: 28px; }
.btn {
  display: inline-flex; flex-direction: column; justify-content: center;
  min-height: 60px; padding: 8px 26px;
  border-radius: 16px; text-decoration: none;
}
.btn-main { background: var(--orange); color: var(--slate); box-shadow: 0 4px 0 var(--orange-dark); }
.btn-main:hover { background: #ff9a3d; }
.btn-main:active { transform: translateY(3px); box-shadow: 0 1px 0 var(--orange-dark); }
.btn-title { font-weight: 800; font-size: 1.15rem; line-height: 1.25; }
.btn-sub { font-size: 0.85rem; opacity: 0.8; line-height: 1.3; }
.btn-quiet { font-weight: 600; text-underline-offset: 4px; }

.hero-shot { margin: 0; }
.hero-shot img {
  border-radius: 18px;
  border: 6px solid #fff;
  box-shadow: 0 30px 60px -30px rgba(22, 60, 90, 0.55);
  transform: rotate(1.2deg);
}

/* --- Code Lab: the training field ------------------------------------------ */

.field {
  color: #fff;
  background-color: var(--field);
  background-image:
    linear-gradient(rgba(255,255,255,.32) 2px, transparent 2px),
    linear-gradient(90deg, rgba(255,255,255,.32) 2px, transparent 2px),
    linear-gradient(rgba(255,255,255,.1) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.1) 1px, transparent 1px);
  background-size: 200px 200px, 200px 200px, 40px 40px, 40px 40px;
  background-position: -1px -1px;
}
.field-inner { max-width: calc(var(--page) + 2 * var(--gutter)); margin: 0 auto; padding: clamp(48px, 7vw, 96px) var(--gutter); }
.field-head { max-width: 40em; }
.field-head h2 { font-size: var(--step-3); font-family: var(--text); font-weight: 900; }
html[data-lang="en"] .field-head h2 { font-family: var(--display); font-weight: 400; }
.field-head p { margin-top: 14px; font-size: 1.1rem; font-weight: 500; text-shadow: 0 1px 2px rgba(0,0,0,.35); }
.path-note { font-weight: 500; }
/* Text sits on solid turf so the grid lines never run through it. */
.field-head p > span, .path-note > span, .field-head h2 > span, .path h3 > span {
  background: var(--field);
  -webkit-box-decoration-break: clone; box-decoration-break: clone;
  box-shadow: 0 0 0 4px var(--field);
}

.demo {
  display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 24px; margin-top: 36px;
}
.demo-code {
  display: flex; flex-direction: column; gap: 14px;
  background: var(--slate); border-radius: 20px; padding: 18px;
  min-height: 420px;
}
.demo-tabs { display: flex; gap: 6px; }
.demo-tabs button {
  font: inherit; font-weight: 700; cursor: pointer;
  border: 0; border-radius: 10px; padding: 6px 16px;
  background: rgba(255,255,255,.08); color: #b9c4cd;
}
.demo-tabs button[aria-selected="true"] { background: rgba(255,255,255,.18); color: #fff; }

/* Blocks, drawn like the game's (and Scratch's) puzzle pieces. */
.blocks, .blk-mouth { list-style: none; margin: 0; padding: 0; }
.blocks { flex: 1; font-weight: 700; font-size: 1.05rem; }
.blk {
  position: relative; width: fit-content; min-width: 9em;
  padding: 8px 16px; margin-bottom: 4px;
  border-radius: 6px; color: #fff;
  transition: filter .15s, box-shadow .15s;
}
.blk b { display: inline-block; min-width: 2.4em; margin: 0 4px; padding: 0 8px; border-radius: 999px; background: #fff; color: var(--slate); text-align: center; }
.blk.hat { background: var(--block-hat); color: var(--slate); border-radius: 18px 18px 6px 6px; padding-top: 12px; }
.blk.flight { background: var(--block-blue); }
.blk.action { background: var(--block-purple); }
.blk.control { background: var(--block-orange); color: var(--slate); padding: 8px 0 14px 0; min-width: 14em; }
.blk.control > .blk-line { display: block; padding: 0 16px 8px; }
.blk-mouth { margin-left: 18px; }
.blk-mouth .blk { margin-bottom: 4px; }
.blk.on { filter: brightness(1.18); box-shadow: 0 0 0 3px #fff, 0 0 18px 4px rgba(255,255,255,.55); z-index: 1; }
.blk.control.on { box-shadow: 0 0 0 3px #fff; filter: none; }

.python {
  flex: 1; margin: 0; padding: 12px 14px; overflow-x: auto;
  font-family: var(--code); font-size: 1rem; line-height: 1.85;
  background: #0b131b; border-radius: 12px; color: #e6edf3;
}
.python .ln { display: block; padding: 0 6px; border-radius: 4px; white-space: pre; }
.python .ln.c { color: #93a0ad; }
.python i { font-style: normal; color: #ff8a1f; }
.python em { font-style: normal; color: #ffcc66; }
.python .ln.on { background: rgba(255,255,255,.16); }

.run {
  align-self: flex-start; display: inline-flex; align-items: center; gap: 10px;
  font: inherit; font-family: var(--display); font-size: 1.2rem; cursor: pointer;
  border: 2px solid rgba(255,255,255,.35); border-radius: 999px;
  padding: 10px 28px; color: #fff; background: #37c24f;
}
html[data-lang="zh"] .run { font-family: var(--text); font-weight: 900; }
.run:hover { background: #45d35d; }
.run[data-running="true"] { background: #ff4d4d; }
.run-icon { width: 0; height: 0; border-left: 14px solid #fff; border-top: 9px solid transparent; border-bottom: 9px solid transparent; }
.run[data-running="true"] .run-icon { width: 14px; height: 14px; border: 0; background: #fff; border-radius: 2px; }

.demo-field {
  display: flex; flex-direction: column; gap: 10px;
  background: rgba(0, 0, 0, 0.18); border-radius: 20px; padding: 18px;
}
.demo-field svg { width: 100%; aspect-ratio: 1; border-radius: 10px; background: var(--field-dark); }
.demo-caption { font-size: 0.95rem; color: #e9f7ee; min-height: 1.7em; }

.path { margin-top: clamp(48px, 7vw, 88px); max-width: 52em; }
.path h3 { font-size: var(--step-2); }
.path-note { margin-top: 10px; max-width: 40em; }
.steps-path {
  list-style: none; counter-reset: step; margin: 22px 0; padding: 0;
  display: flex; flex-wrap: wrap; gap: 10px 8px;
}
.steps-path li {
  counter-increment: step;
  display: flex; align-items: center; gap: 8px;
  padding: 6px 14px 6px 6px; border-radius: 999px;
  background: rgba(255,255,255,.95); color: var(--slate); font-weight: 700; font-size: 0.98rem;
}
.steps-path li::before {
  content: counter(step);
  display: grid; place-items: center; width: 28px; height: 28px; border-radius: 50%;
  background: var(--slate); color: #fff; font-family: var(--display); font-size: 0.85rem;
}
.steps-path li:last-child::before { background: var(--orange); color: var(--slate); }

.field-shot { margin: clamp(32px, 5vw, 64px) 0 0; }
.field-shot img { border-radius: 16px; border: 6px solid rgba(255,255,255,.9); }

/* --- Flying -------------------------------------------------------------------- */

.fly { padding: clamp(56px, 8vw, 110px) var(--gutter); max-width: calc(var(--page) + 2 * var(--gutter)); margin: 0 auto; }
.fly-head { max-width: 42em; }
.fly-head p { margin-top: 14px; }

.modes { width: 100%; margin-top: 36px; border-collapse: collapse; }
.modes th, .modes td { text-align: left; padding: 16px 12px; vertical-align: middle; }
.modes thead th { font-size: 0.85rem; color: var(--slate-soft); font-weight: 600; border-bottom: 2px solid var(--slate); }
.modes tbody tr { border-bottom: 1px solid #d6e2ea; }
.modes tbody th { font-size: 1.15rem; white-space: nowrap; }
.modes td:nth-child(2) { color: #34475a; max-width: 30em; }
.m-label { display: none; }
/* Five-segment bars, like the flight-style cards in the game's menu. */
.meter {
  display: block; width: 110px; height: 10px;
  background:
    linear-gradient(90deg, var(--orange) calc(var(--v) * 20%), transparent 0),
    repeating-linear-gradient(90deg, #d9e3ea 0 18px, transparent 18px 22px);
  -webkit-mask: repeating-linear-gradient(90deg, #000 0 18px, transparent 18px 22px);
          mask: repeating-linear-gradient(90deg, #000 0 18px, transparent 18px 22px);
}

.strip {
  display: grid; grid-auto-flow: column; grid-auto-columns: min(560px, 85vw);
  gap: 18px; margin-top: 44px; padding-bottom: 14px;
  overflow-x: auto; scroll-snap-type: x mandatory; overscroll-behavior-x: contain;
}
.strip figure { margin: 0; scroll-snap-align: start; }
.strip img { border-radius: 14px; }
.strip figcaption { margin-top: 8px; font-size: 0.95rem; color: var(--slate-soft); }

/* --- Teachers -------------------------------------------------------------------- */

.teachers {
  padding: clamp(56px, 8vw, 110px) var(--gutter);
  background: var(--slate); color: #eef3f6;
}
.teachers h2 { max-width: var(--page); margin: 0 auto; }
.features {
  max-width: var(--page); margin: 32px auto 0;
  display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 300px), 1fr));
  gap: 30px 48px;
}
.features div { border-left: 3px solid var(--orange); padding-left: 16px; }
.features dt { font-weight: 800; font-size: 1.12rem; }
.features dd { margin: 6px 0 0; color: #b9c6d0; }

/* --- Download ------------------------------------------------------------------------ */

.download { padding: clamp(56px, 8vw, 110px) var(--gutter); max-width: calc(var(--page) + 2 * var(--gutter)); margin: 0 auto; }
.download-note { margin-top: 10px; color: var(--slate-soft); }
.platforms { display: grid; grid-template-columns: 1fr 1fr 0.8fr; gap: 22px; margin-top: 32px; align-items: start; }
.platform { padding: 24px; border-radius: 20px; background: #fff; border: 2px solid #dbe6ee; }
.platform h3 { margin-bottom: 18px; }
.platform.is-yours { border-color: var(--orange); box-shadow: 0 0 0 4px rgba(255, 138, 31, 0.18); }
.platform .yours-tag { display: inline-block; margin-bottom: 10px; padding: 2px 10px; border-radius: 999px; background: var(--orange); color: var(--slate); font-size: 0.82rem; font-weight: 700; }
.platform-off { background: transparent; border-style: dashed; color: var(--slate-soft); }
.platform-off h3 { color: var(--slate); }
.alt { margin-top: 14px; font-size: 0.95rem; color: var(--slate-soft); }
.alt a { color: var(--slate); font-weight: 700; }
.install { margin: 18px 0 0; padding-left: 1.4em; }
.install li { margin-bottom: 8px; padding-left: 4px; }
.install li::marker { font-family: var(--display); color: var(--orange-dark); }
.req { margin-top: 14px; font-size: 0.92rem; color: var(--slate-soft); }
.all-versions { margin-top: 28px; }
.all-versions a { font-weight: 600; text-underline-offset: 4px; }

.foot { border-top: 1px solid #dbe6ee; padding: 36px var(--gutter) 48px; }
.foot-inner { max-width: var(--page); margin: 0 auto; display: flex; align-items: center; gap: 24px; }
.foot-logo { width: 66px; height: auto; flex: none; }
.foot-text p { color: var(--slate-soft); font-size: 0.95rem; }
.foot-text .foot-credit { color: var(--slate); font-weight: 700; font-size: 1.05rem; }
.foot-text .foot-small { font-size: 0.85rem; }

/* --- Smaller screens ------------------------------------------------------------------ */

@media (max-width: 960px) {
  .hero { grid-template-columns: 1fr; }
  .hero-shot img { transform: none; }
  .demo { grid-template-columns: 1fr; }
  .demo-code { min-height: 0; }
  .platforms { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .nav a:not(.nav-download) { display: none; }
  .bar { gap: 10px; }
  .brand-name { font-size: 1.1rem; }
  .modes thead { display: none; }
  .modes, .modes tbody, .modes tr { display: block; }
  .modes tbody tr { display: grid; grid-template-columns: auto 1fr; gap: 4px 14px; padding: 14px 0; }
  .modes th, .modes td { padding: 0; }
  .modes tbody th { grid-column: 1 / -1; }
  .modes td:nth-child(2) { grid-column: 1 / -1; }
  .modes td { display: flex; align-items: center; gap: 10px; }
  .modes .m-label { display: inline; font-size: 0.85rem; color: var(--slate-soft); min-width: 3.2em; }
  .blk { min-width: 0; }
  .blk.control { min-width: 0; }
}