:root {
  color: #17213f;
  background: #eff9ff;
  font-family: Arial, Helvetica, sans-serif;
  font-synthesis: none;
  text-rendering: optimizeLegibility;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    linear-gradient(rgba(255, 255, 255, 0.45) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.45) 1px, transparent 1px),
    linear-gradient(135deg, #9df7ff 0%, #fff0a5 48%, #ff99ca 100%);
  background-size: 42px 42px, 42px 42px, auto;
}

a {
  color: inherit;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 3px solid #17213f;
  background: rgba(255, 255, 255, 0.86);
  backdrop-filter: blur(12px);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 14px 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 1000;
  text-decoration: none;
}

.brand img {
  width: 44px;
  height: 44px;
  border: 3px solid #17213f;
  border-radius: 12px;
  box-shadow: 0 3px 0 #17213f;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.nav-links a,
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 42px;
  padding: 0.7rem 1rem;
  border: 3px solid #17213f;
  border-radius: 14px;
  background: #ffffff;
  color: #17213f;
  font-weight: 1000;
  text-decoration: none;
  box-shadow: 0 4px 0 #17213f;
}

.nav-links a.primary,
.button.primary {
  background: linear-gradient(180deg, #ffe96f, #ffb11f);
}

.hero {
  position: relative;
  display: grid;
  align-items: end;
  min-height: 78vh;
  overflow: hidden;
  border-bottom: 4px solid #17213f;
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    linear-gradient(90deg, rgba(20, 184, 255, 0.55), rgba(255, 70, 158, 0.45)),
    url("assets/number-duel-splash.webp") center / cover no-repeat;
}

.hero::after {
  content: "";
  position: absolute;
  inset: auto 0 0;
  height: 38%;
  background: linear-gradient(0deg, rgba(18, 27, 55, 0.92), transparent);
}

.hero-content {
  position: relative;
  z-index: 1;
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 92px 0 46px;
  color: #ffffff;
  text-shadow: 0 4px 0 rgba(18, 27, 55, 0.35);
}

.eyebrow {
  margin: 0 0 12px;
  color: #ffdd3f;
  font-weight: 1000;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  margin: 0;
  color: #17213f;
  line-height: 1.02;
}

.hero h1 {
  max-width: 760px;
  color: #ffffff;
  font-size: clamp(3rem, 10vw, 7rem);
}

.hero p {
  max-width: 620px;
  margin: 18px 0 0;
  font-size: clamp(1.05rem, 2.2vw, 1.35rem);
  font-weight: 900;
  line-height: 1.45;
}

.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 24px;
  text-shadow: none;
}

.hero-actions .button:not(.primary) {
  background: linear-gradient(180deg, #ffffff, #eaf4ff);
}

.section {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 46px 0;
}

.section h2 {
  font-size: clamp(2rem, 5vw, 3.4rem);
}

.section-copy {
  max-width: 720px;
  margin: 12px 0 0;
  color: #3b4868;
  font-size: 1.05rem;
  font-weight: 800;
  line-height: 1.55;
}

.feature-grid,
.difficulty-grid,
.policy-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  margin-top: 24px;
}

.card,
.content-card {
  border: 4px solid #17213f;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.94);
  box-shadow: 0 8px 0 #17213f;
}

.card {
  padding: 20px;
}

.card h3 {
  font-size: 1.45rem;
}

.card p,
.content-card p,
.content-card li {
  color: #3b4868;
  font-weight: 800;
  line-height: 1.6;
}

.difficulty-card {
  min-height: 160px;
  padding: 18px;
  border-top: 16px solid var(--accent);
}

.difficulty-card strong {
  display: block;
  margin-top: 14px;
  color: #17213f;
  font-size: 2rem;
}

.cta-band {
  margin: 34px 0 8px;
  padding: 26px;
  border: 4px solid #17213f;
  border-radius: 8px;
  background: linear-gradient(135deg, #fff8db, #dff8ff);
  box-shadow: 0 8px 0 #17213f;
}

.cta-band h2 {
  font-size: clamp(2rem, 5vw, 3.2rem);
}

.page-hero {
  width: min(960px, calc(100% - 32px));
  margin: 0 auto;
  padding: 58px 0 24px;
}

.page-hero h1 {
  font-size: clamp(2.4rem, 7vw, 5rem);
}

.content-card {
  width: min(960px, calc(100% - 32px));
  margin: 0 auto 42px;
  padding: 28px;
}

.content-card h2 {
  margin-top: 30px;
  font-size: 1.8rem;
}

.content-card h2:first-child {
  margin-top: 0;
}

.content-card a {
  color: #245ac4;
  font-weight: 1000;
}

.site-footer {
  border-top: 4px solid #17213f;
  background: #17213f;
  color: #ffffff;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 22px 0;
  font-weight: 900;
}

.footer-inner a {
  color: #ffffff;
}

@media (max-width: 760px) {
  .nav {
    align-items: flex-start;
  }

  .nav-links {
    gap: 8px;
  }

  .nav-links a {
    min-height: 36px;
    padding: 0.55rem 0.7rem;
    font-size: 0.82rem;
  }

  .hero {
    min-height: 74vh;
  }

  .feature-grid,
  .difficulty-grid,
  .policy-grid {
    grid-template-columns: 1fr;
  }

  .footer-inner {
    flex-direction: column;
  }
}