* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
html {
  scroll-behavior: smooth;
}

body {
  font-family: sans-serif;
  margin: 0;
}
.container {
  display: flex;
  gap: 1.5rem;
  padding: 1rem;
}
.sidebar {
  width: 300px;
  flex-grow: 0;
  flex-shrink: 0;
  flex-basis: 300px;
  padding: 1rem;
  background: #f5f5f5;
  border-radius: 8px;
  position: sticky;
  top: 1rem;
  max-height: calc(100vh - 2rem);
  overflow: auto;
}
.content {
  flex-grow: 1;
  flex-shrink: 1;
  flex-basis: auto;
  max-width: 800px;
}
section {
  padding: 2rem;
  margin-bottom: 2rem;
  background: white;
  border: 1px solid #e0e0e0;
  border-radius: 8px;
  scroll-margin-top: 1rem;
  position: relative;
}
.deco {
  position: absolute;
  opacity: 0.6;
  pointer-events: none;
}

.deco img {
  width: 150px;
  height: auto;
}
#deco-1 {
  top: -10%;
  left: -5%;
}
#deco-2 {
  top: 50%;
  right: -5%;
}
#deco-3 {
  bottom: -10%;
  left: 50%;
}
#deco-4 {
  top: 10%;
  right: 15%;
}
#deco-5 {
  bottom: 5%;
  left: 10%;
}
nav a:focus-visible {
  outline: 2px solid #3b82f6;
  outline-offset: 2px;
  border-radius: 4px;
}
.back-to-top {
  display: inline-block;
  margin-top: 2rem;
  padding: 0.5rem 1rem;
  background-color: #3b82f6;
  color: white;
  border-radius: 4px;
  text-decoration: none;
  transition: background-color 0.2s ease;
}
.back-to-top:hover {
  background-color: #2563eb;
}