html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: #f3f4f6;
  color: #1f2937;
  line-height: 1.6;
}

h1 {
  margin-top: 0;
  margin-bottom: 10px;
  font-size: 36px;
  color: #111827;
}

h2 {
  margin-top: 0;
  margin-bottom: 20px;
  font-size: 26px;
  color: #111827;
}

p {
  font-size: 18px;
  margin-top: 0;
  margin-bottom: 16px;
}

ol {
  padding-left: 22px;
  margin: 0;
}

img {
  display: block;
  max-width: 100%;
  margin: 18px auto;
  border-radius: 12px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
}

.container {
  max-width: 900px;
  margin: 40px auto;
  padding: 32px;
  background: #ffffff;
  border-radius: 20px;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.08);
}

section {
  background: #f9fafb;
  padding: 24px;
  border-radius: 16px;
  margin-top: 24px;
  border: 1px solid #e5e7eb;
}

nav {
  margin-top: 24px;
  background: #eff6ff;
  padding: 18px;
  border-radius: 16px;
  border: 1px solid #dbeafe;
}

nav a {
  display: block;
  padding: 12px 14px;
  text-decoration: none;
  color: #1d4ed8;
  font-weight: 600;
  border-radius: 10px;
  transition: background 0.25s, color 0.25s, transform 0.25s;
}

nav a + a {
  margin-top: 10px;
}

li {
  margin-bottom: 14px;
}

ol > li {
  background: #ffffff;
  padding: 16px;
  border-radius: 12px;
  margin-bottom: 16px;
  border: 1px solid #eceff3;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.04);
}

li img {
  margin-top: 20px;
}

.caption {
  margin-top: -4px;
  margin-bottom: 0;
  font-size: 14px;
  color: #6b7280;
  text-align: center;
}

a {
  color: #2563eb;
}

a:hover {
  color: #1d4ed8;
}

.back-to-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: #2563eb;
  color: white;
  text-decoration: none;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 26px;
  line-height: 1;
  box-shadow: 0 10px 24px rgba(37, 99, 235, 0.35);
  transition: background 0.25s, transform 0.25s, box-shadow 0.25s;
  -webkit-tap-highlight-color: transparent;
}
@media (hover: hover) {
  .back-to-top:hover {
    background: #1d4ed8;
    transform: translateY(-3px);
    box-shadow: 0 14px 30px rgba(37, 99, 235, 0.4);
  }

  nav a:hover {
    background: #dbeafe;
    color: #1e3a8a;
    transform: translateX(4px);
  }
}


@media (max-width: 600px) {

  .container {
    padding: 18px;
  }

  img {
    margin: 16px auto;
  }

  .back-to-top {
    width: 60px;
    height: 60px;
    font-size: 28px;
  }

}

.back-to-top,
.back-to-top:visited,
.back-to-top:hover,
.back-to-top:active,
.back-to-top:focus {
  color: white;
  text-decoration: none;
}