:root {
  --bg: #0e1117;
  --bg-section: #161b22;
  --bg-card: #1f2633;
  --text: #e6edf3;
  --text-soft: #9da7b3;
  --accent: #5b9dff;
  --border: #2b3442;
  --header-h: 72px;
  --footer-h: 64px;
}

body.light {
  --bg: #f4f6f8;
  --bg-section: #ffffff;
  --bg-card: #f0f2f5;
  --text: #1f2328;
  --text-soft: #5f6b7a;
  --accent: #005fcc;
  --border: #d0d7de;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  min-height: 100%;
}

body {
  font-family: "Segoe UI", system-ui, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  padding-top: var(--header-h);
  padding-bottom: var(--footer-h);
}

/* HEADER */
.site-header {
  position: fixed;
  top: 0;
  width: 100%;
  height: var(--header-h);
  background: var(--bg-section);
  border-bottom: 1px solid var(--border);
  z-index: 1000;
}

.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  height: 100%;
  padding: 0 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  text-decoration: none;
  font-weight: 700;
  font-size: 18px;
}

.header-logo {
  height: 36px;
}

/* NAV */
nav a {
  color: var(--text);
  text-decoration: none;
  margin-left: 20px;
  font-weight: 500;
}

nav a:hover {
  color: var(--accent);
}

/* FOOTER */
.site-footer {
  position: fixed;
  bottom: 0;
  width: 100%;
  height: var(--footer-h);
  background: var(--bg-section);
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  color: var(--text-soft);
}

/* CONTENT */
.site-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 64px 20px 96px;
}

/* HERO */
.hero {
  text-align: center;
  margin-bottom: 80px;
}

.hero h1 {
  font-size: 40px;
  margin-bottom: 16px;
}

.hero p {
  max-width: 720px;
  margin: 0 auto;
  font-size: 17px;
  color: var(--text-soft);
}

/* FEATURES */
.features {
  background: var(--bg-section);
  border-radius: 28px;
  padding: 64px;
  margin-bottom: 96px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.feature {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 28px;
}

/* SUPPORT */
.support {
  background: linear-gradient(135deg, var(--bg-card), var(--bg-section));
  border-radius: 28px;
  padding: 72px;
  border: 1px solid var(--border);
}

/* THEME BUTTON */
#themeToggle {
  position: fixed;
  right: 16px;
  bottom: calc(var(--footer-h) + 16px);
  width: 52px;
  height: 52px;
  border-radius: 50%;
  border: none;
  background: var(--bg-section);
  color: var(--text);
  font-size: 22px;
  cursor: pointer;
  z-index: 2000;
}

/* MOBILE */
@media (max-width: 900px) {
  .features {
    grid-template-columns: 1fr;
    padding: 36px;
  }
}

@media (max-width: 600px) {
  .hero h1 {
    font-size: 30px;
  }
  .features {
    padding: 28px 20px;
  }
  .support {
    padding: 40px 24px;
  }
}