body {
  margin: 0;
  font-family: Arial, "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
  background: #f4f7fb;
  color: #222;
}

header {
  text-align: center;
  padding: 28px 12px;
  background: #1f2937;
  color: white;
}

header h1 {
  margin: 0 0 8px;
  font-size: 32px;
}

nav {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
  padding: 18px;
  background: white;
}

nav a {
  padding: 10px 14px;
  border-radius: 999px;
  background: #e5e7eb;
  color: #111;
  text-decoration: none;
  font-weight: bold;
}

nav a.active {
  background: #2563eb;
  color: white;
}

main {
  display: grid;
  grid-template-columns: 1fr 300px;
  gap: 24px;
  max-width: 1100px;
  margin: 30px auto;
  padding: 0 16px;
}

.quiz-box {
  background: white;
  padding: 28px;
  border-radius: 18px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.08);
}

.status {
  display: flex;
  justify-content: space-between;
  font-weight: bold;
  margin-bottom: 14px;
}

.progress {
  height: 12px;
  background: #e5e7eb;
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 24px;
}

#progressBar {
  height: 100%;
  width: 0%;
  background: #22c55e;
  transition: 0.3s;
}

#question {
  font-size: 26px;
  margin-bottom: 24px;
}

#choices {
  display: grid;
  gap: 12px;
}

#choices button {
  padding: 16px;
  font-size: 18px;
  border: none;
  border-radius: 12px;
  background: #f1f5f9;
  cursor: pointer;
  font-weight: bold;
}

#choices button:hover {
  background: #dbeafe;
}

#choices button.correct {
  background: #86efac;
}

#choices button.wrong {
  background: #fca5a5;
}

#result {
  font-size: 20px;
  font-weight: bold;
  margin-top: 20px;
}

.ad-box {
  background: white;
  padding: 16px;
  border-radius: 16px;
  text-align: center;
  min-height: 280px;
}

@media (max-width: 800px) {
  main {
    grid-template-columns: 1fr;
  }
}

nav button {
  padding: 10px 14px;
  border-radius: 999px;
  background: #e5e7eb;
  color: #111;
  border: none;
  font-weight: bold;
  cursor: pointer;
}

nav button.active {
  background: #2563eb;
  color: white;
}