body {
  font-family: Segoe UI, Arial, sans-serif;
  line-height: 1.6;
  margin: 0;
  color: #222;
  background: #fdfdfd;
}
header {
  background: #04AA6D;
  color: #fff;
  padding: 24px 32px;
}
header h1 { margin: 0 0 8px 0; }
header nav a, header a { color: #fff; }
main {
  max-width: 860px;
  margin: 0 auto;
  padding: 24px 32px 60px 32px;
}
pre {
  background: #f4f4f4;
  border-left: 4px solid #04AA6D;
  padding: 12px 16px;
  overflow-x: auto;
  border-radius: 4px;
}
code {
  background: #f4f4f4;
  padding: 2px 5px;
  border-radius: 3px;
  font-family: Consolas, monospace;
}
pre code { background: none; padding: 0; }
.intro { font-size: 1.05em; color: #444; }
.exercise-box, .question-box {
  background: #eef9f3;
  border: 1px solid #cdeee0;
  border-radius: 6px;
  padding: 16px 20px;
  margin-top: 28px;
}
.exercise-box ul { margin: 8px 0 0 0; }
.topic-list { columns: 2; column-gap: 40px; }
.topic-list li { margin-bottom: 6px; break-inside: avoid; }
textarea { width: 100%; max-width: 500px; font-family: Consolas, monospace; }
footer { max-width: 860px; margin: 0 auto; padding: 0 32px 40px 32px; }
a { color: #04AA6D; text-decoration: none; }
a:hover { text-decoration: underline; }

.badge {
  display: inline-block;
  background: #056b45;
  color: #fff;
  font-size: 0.75em;
  padding: 2px 10px;
  border-radius: 12px;
  margin-bottom: 8px;
}
table { border-collapse: collapse; width: 100%; margin: 12px 0; }
table th, table td {
  border: 1px solid #ddd;
  padding: 8px 10px;
  text-align: left;
}
table th { background: #f0f0f0; }
.note { color: #666; font-size: 0.9em; margin-top: 24px; }