@import url('https://itproger.com/css/main-font.css');
body {
  margin: 0;
  font-family:Montserrat,sans-serif;
  background-color: #f3f4f6;
  display: flex;
  min-height: 100vh;
}
.sidebar {
  width: 250px;
  height: 100vh;
  background: #fff;
  padding: 20px;
  padding-bottom: 0px;
  box-shadow: 2px 0 8px rgba(0, 0, 0, 0.1);
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: #3b82f6 #e5e7eb;
}
.sidebar::-webkit-scrollbar {
  width: 8px;
}
.sidebar::-webkit-scrollbar-thumb {
  background-color: #3b82f6;
  border-radius: 10px;
}
.sidebar h2 {
  font-size: 20px;
  margin-bottom: 10px;
}
.sidebar a {
  display: inline-block;
  margin-bottom: 20px;
  color: #3b82f6;
  text-decoration: none;
  font-weight: bold;
}
a.sub_link {margin-bottom: 0}
a.sub_link:hover {text-decoration: underline}
.sidebar a:hover {color: #2759aa}
.sidebar button {
  display: block;
  width: 100%;
  margin-bottom: 10px;
  padding: 10px;
  background: #e5e7eb;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  text-align: left;
}
.sidebar button.active {
  background: #3b82f6;
  color: white;
}
#question-nav {margin-bottom: 70px}
.main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 40px;
}
.card {
  background: white;
  padding: 30px;
  border-radius: 20px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
  width: 100%;
  max-width: 600px;
}
.card h1 {
  font-size: 24px;
  margin-bottom: 20px;
}
.option {
  display: block;
  width: 100%;
  padding: 12px;
  margin-bottom: 10px;
  border: 2px solid transparent;
  border-radius: 10px;
  background: #f9fafb;
  cursor: pointer;
  transition: all 0.2s;
}
.option:hover {
  background: #e5e7eb;
}
.option.correct {
  border-color: #22c55e;
  color: #16a34a;
}
.option.wrong {
  border-color: #ef4444;
  color: #b91c1c;
}
.result {
  margin-top: 20px;
  font-weight: bold;
}

@media(max-width: 900px) {
    body {flex-direction: column;}
    .sidebar {height: 300px; width: 96%; padding: 20px 2%;}
    .main {padding: 15px;}
}