* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --teal: #5bc8a8;
  --cyan: #3ab8d8;
  --blue: #2a8fc4;
  --bg: #080f14;
  --text: #e0e0e0;
  --text-muted: #888;
  --nav-bg: rgba(8, 15, 20, 0.88);
  --card-bg: rgba(255, 255, 255, 0.04);
  --card-border: rgba(255, 255, 255, 0.07);
  --grid-color: rgba(58, 184, 216, 0.07);
}

body.light-mode {
  --bg: #f4f7f9;
  --text: #1a2a3a;
  --text-muted: #556677;
  --nav-bg: rgba(244, 247, 249, 0.9);
  --card-bg: #ffffff;
  --card-border: rgba(0, 0, 0, 0.05);
  --grid-color: rgba(58, 184, 216, 0.04);
}

body {
  font-family: "Segoe UI", sans-serif;
  background-color: var(--bg);
  color: var(--text);
  min-height: 100vh;
  transition:
    background-color 0.3s,
    color 0.3s;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(var(--grid-color) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-color) 1px, transparent 1px);
  background-size: 50px 50px;
  pointer-events: none;
  z-index: 0;
}

nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.9rem 2rem;
  background: var(--nav-bg);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(58, 184, 216, 0.15);
}

.logo img {
  height: 38px;
  width: auto;
  display: block;
}

.nav-right {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.back-link {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.85rem;
  letter-spacing: 1px;
  text-transform: uppercase;
  transition: color 0.3s;
}

.back-link:hover {
  color: var(--cyan);
}

.theme-toggle {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text);
  width: 38px;
  height: 38px;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  transition: all 0.3s;
}

.theme-toggle:hover {
  border-color: var(--cyan);
  transform: scale(1.1);
}

.demo-intro {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin: 0 auto;
  padding: 3rem 2rem 1.5rem;
  text-align: center;
}

.demo-intro .label {
  font-size: 0.75rem;
  letter-spacing: 4px;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 0.75rem;
}

.demo-intro h1 {
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  font-weight: 800;
  margin-bottom: 0.9rem;
  line-height: 1.15;
}

.demo-intro h1 span {
  background: linear-gradient(135deg, var(--teal), var(--cyan), var(--blue));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.demo-intro p {
  color: var(--text-muted);
  max-width: 640px;
  margin: 0 auto;
  line-height: 1.7;
}

.btn {
  display: inline-block;
  padding: 0.85rem 2rem;
  border-radius: 6px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.3s;
  letter-spacing: 0.5px;
}

.btn-primary {
  background: linear-gradient(135deg, var(--teal), var(--blue));
  color: #fff;
  border: none;
  box-shadow: 0 0 20px rgba(58, 184, 216, 0.3);
}

.btn-primary:hover {
  box-shadow: 0 0 35px rgba(58, 184, 216, 0.5);
  transform: translateY(-2px);
}

footer {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 2.5rem;
  border-top: 1px solid var(--card-border);
  color: var(--text-muted);
  font-size: 0.85rem;
}

footer span {
  color: var(--teal);
}

footer a {
  color: var(--cyan);
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}