:root {
  --bg: #070b1a;
  --panel: #121a33;
  --text: #e8eefc;
  --muted: #b6c5f4;
  --accent: #4fc3ff;
  --accent-2: #7bffb8;
  --shadow: 0 15px 35px rgba(0, 0, 0, 0.35);
}

body.light {
  --bg: #f2f6ff;
  --panel: #ffffff;
  --text: #11203c;
  --muted: #4b5e84;
  --accent: #1a78ff;
  --accent-2: #00b36b;
  --shadow: 0 10px 30px rgba(40, 72, 126, 0.15);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  font-family: "Segoe UI", Arial, sans-serif;
  background: radial-gradient(circle at top, #131d3f 0%, var(--bg) 45%);
  color: var(--text);
  scroll-behavior: smooth;
}

body.light {
  background: linear-gradient(135deg, #eef3ff 0%, #f9fcff 100%);
}

.hero {
  text-align: center;
  padding: 3rem 1rem 2rem;
}

.tag {
  color: var(--accent-2);
  text-transform: uppercase;
  letter-spacing: 0.2rem;
  font-weight: 700;
}

h1 {
  font-size: clamp(1.8rem, 3.2vw, 3rem);
  margin: 0.4rem 0;
}

.subtitle {
  max-width: 760px;
  margin: 0 auto 1rem;
  color: var(--muted);
}

.btn {
  border: 1px solid transparent;
  border-radius: 999px;
  padding: 0.7rem 1.2rem;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  color: #001028;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, filter 0.2s ease;
}

.btn:hover {
  transform: translateY(-2px) scale(1.03);
  box-shadow: var(--shadow);
  filter: brightness(1.05);
}

.progress-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.7rem;
  backdrop-filter: blur(8px);
  background: color-mix(in srgb, var(--bg) 80%, transparent);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.progress-nav a {
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  display: grid;
  place-items: center;
  color: var(--text);
  text-decoration: none;
  background: rgba(255, 255, 255, 0.08);
  transition: transform 0.2s ease, background 0.25s ease;
}

.progress-nav a:hover,
.progress-nav a.active {
  background: var(--accent);
  color: #00142e;
  transform: scale(1.12);
}

.slides {
  max-width: 1000px;
  margin: 0 auto;
  padding: 1rem;
}

.slide {
  margin: 1.2rem 0;
  padding: 1.3rem;
  border-radius: 18px;
  background: color-mix(in srgb, var(--panel) 85%, transparent);
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: var(--shadow);
  transform: translateY(24px);
  opacity: 0;
  transition: transform 0.6s ease, opacity 0.6s ease, border-color 0.3s ease;
}

.slide.visible {
  transform: translateY(0);
  opacity: 1;
}

.slide:hover {
  border-color: color-mix(in srgb, var(--accent) 50%, #ffffff 10%);
}

.slide-number {
  display: inline-block;
  margin-bottom: 0.3rem;
  color: var(--accent-2);
  font-weight: 700;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}

.card {
  position: relative;
  overflow: hidden;
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 14px;
  padding: 1rem;
  transition:
    transform 0.3s ease,
    background 0.3s ease,
    opacity 0.3s ease,
    filter 0.3s ease,
    border-color 0.3s ease;
}

.card::before {
  content: "";
  position: absolute;
  inset: -35%;
  pointer-events: none;
  background: radial-gradient(
    220px circle at var(--mx, 50%) var(--my, 50%),
    rgba(79, 195, 255, 0.24),
    transparent 70%
  );
  opacity: 0;
  transition: opacity 0.25s ease;
}

.card:hover {
  transform: translateY(-6px) scale(1.02);
  background: rgba(79, 195, 255, 0.15);
  border-color: rgba(79, 195, 255, 0.55);
}

.card:hover::before,
.card.active-card::before {
  opacity: 1;
}

.grid.has-focus .card {
  opacity: 0.5;
  transform: scale(0.98);
  filter: saturate(0.85);
}

.grid.has-focus .card.active-card {
  opacity: 1;
  transform: translateY(-7px) scale(1.03);
  filter: saturate(1.1);
  box-shadow: 0 16px 30px rgba(0, 0, 0, 0.24);
}

.grid.has-focus .card.active-card.enter-from-right {
  animation: cardFromRight 0.3s ease;
}

.grid.has-focus .card.active-card.enter-from-left {
  animation: cardFromLeft 0.3s ease;
}

@keyframes cardFromRight {
  0% {
    transform: translateX(20px) translateY(-7px) scale(1);
  }
  100% {
    transform: translateX(0) translateY(-7px) scale(1.03);
  }
}

@keyframes cardFromLeft {
  0% {
    transform: translateX(-20px) translateY(-7px) scale(1);
  }
  100% {
    transform: translateX(0) translateY(-7px) scale(1.03);
  }
}

.answer,
.highlight {
  color: var(--accent-2);
  font-weight: 700;
}

.timeline {
  display: grid;
  gap: 0.8rem;
}

.step {
  padding: 0.8rem;
  border-left: 4px solid var(--accent);
  background: rgba(255, 255, 255, 0.04);
  border-radius: 8px;
}

ul,
ol {
  margin: 0.8rem 0 0.2rem 1.2rem;
}

.interactive-slide {
  text-align: center;
}

.counter {
  font-size: 1.1rem;
}

.pulse {
  animation: pulse 1.8s infinite;
}

@keyframes pulse {
  0%,
  100% {
    box-shadow: 0 0 0 0 rgba(79, 195, 255, 0.45);
  }
  50% {
    box-shadow: 0 0 0 16px rgba(79, 195, 255, 0);
  }
}

.powered-device {
  margin-top: 0.6rem;
  font-size: 1.05rem;
  font-style: italic;
  color: var(--accent-2);
  min-height: 1.6em;
  transition: opacity 0.25s ease;
}

.video-link {
  display: inline-block;
  margin-top: 1rem;
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  background: color-mix(in srgb, var(--accent) 15%, transparent);
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  border: 1px solid color-mix(in srgb, var(--accent) 30%, transparent);
  transition: transform 0.2s ease, background 0.25s ease, color 0.25s ease;
}

.video-link:hover {
  transform: translateY(-2px) scale(1.03);
  background: var(--accent);
  color: #00142e;
}

footer {
  text-align: center;
  color: var(--muted);
  padding: 1.5rem 1rem 2rem;
}