:root {
  --bg: #eff4ff;
  --surface: #ffffff;
  --text: #11203a;
  --muted: #516180;
  --primary: #1f6fff;
  --primary-deep: #0d4dcc;
  --line: #d8e2ff;
  --shadow: 0 14px 32px rgba(19, 57, 133, 0.14);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Trebuchet MS", "Segoe UI", sans-serif;
  color: var(--text);
  background: radial-gradient(circle at 20% 10%, #dce8ff 0%, var(--bg) 40%, #f7faff 100%);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 14px clamp(16px, 3vw, 40px);
  backdrop-filter: blur(10px);
  background: rgba(239, 244, 255, 0.78);
  border-bottom: 1px solid var(--line);
}

.brand img {
  width: 140px;
  height: auto;
}

nav {
  display: flex;
  gap: 20px;
}

nav a {
  text-decoration: none;
  color: var(--muted);
  font-weight: 700;
}

nav a.active,
nav a:hover {
  color: var(--primary-deep);
}

main {
  width: min(1120px, 92vw);
  margin: 0 auto;
}

.hero {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 34px;
  align-items: center;
  padding: 56px 0 36px;
}

.tag {
  display: inline-block;
  padding: 6px 12px;
  border-radius: 999px;
  background: #dbe8ff;
  color: #204385;
  font-weight: 700;
  letter-spacing: 0.04em;
}

h1 {
  margin: 14px 0 12px;
  font-size: clamp(32px, 4vw, 54px);
  line-height: 1.08;
}

.hero p {
  color: var(--muted);
  font-size: 18px;
}

.hero-image {
  margin: 0;
  background: linear-gradient(145deg, #d9e6ff 0%, #f6f9ff 100%);
  border-radius: 24px;
  padding: 24px;
  box-shadow: var(--shadow);
}

.hero-image img {
  width: 100%;
  display: block;
}

.hero-actions {
  margin-top: 22px;
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.btn {
  text-decoration: none;
  border: none;
  border-radius: 10px;
  padding: 12px 18px;
  font-weight: 700;
  cursor: pointer;
}

.btn.primary {
  color: #fff;
  background: linear-gradient(120deg, var(--primary) 0%, var(--primary-deep) 100%);
}

.btn.ghost {
  color: var(--primary-deep);
  background: #e9f0ff;
}

.platform-switch {
  margin: 16px 0 26px;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.platform-btn {
  border: 1px solid #b8ccff;
  background: #fff;
  color: #345082;
  border-radius: 999px;
  padding: 10px 16px;
  font-weight: 700;
  cursor: pointer;
}

.platform-btn.active {
  color: #fff;
  background: linear-gradient(120deg, #2f7bff, #0f4dc7);
  border-color: transparent;
}

.download-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
}

.download-card {
  background: var(--surface);
  border-radius: 16px;
  border: 1px solid var(--line);
  padding: 22px;
  box-shadow: var(--shadow);
}

.download-card.hidden {
  display: none;
}

.download-card img {
  width: 52px;
  height: 52px;
}

.download-card h2 {
  margin: 14px 0 10px;
  font-size: 22px;
}

.download-card p,
.download-card li {
  color: var(--muted);
}

.download-card ul {
  margin: 0 0 16px;
  padding-left: 18px;
}

.guide {
  margin: 42px 0 60px;
  padding: 26px;
  border-radius: 16px;
  border: 1px solid var(--line);
  background: #f5f8ff;
}

.guide h2 {
  margin: 0 0 18px;
}

.steps {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
}

.steps div {
  background: #fff;
  border-radius: 14px;
  padding: 16px;
}

.steps span {
  font-size: 24px;
  font-weight: 800;
  color: #1d5ad9;
}

.to-top {
  position: fixed;
  right: 20px;
  bottom: 20px;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: none;
  color: #fff;
  background: #134fbf;
  cursor: pointer;
  display: none;
}

footer {
  padding: 24px 0 30px;
  text-align: center;
  color: #6880aa;
}

.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

.reveal.show {
  opacity: 1;
  transform: translateY(0);
}

@media (max-width: 960px) {
  .hero {
    grid-template-columns: 1fr;
  }

  .download-grid,
  .steps {
    grid-template-columns: 1fr;
  }
}