:root {
  --color-primary: #6366f1;
  --color-primary-dark: #3730a3;
  --color-secondary: #22c55e;
  --color-secondary-dark: #15803d;
  --color-danger: #f44336;
  --color-danger-dark: #d32f2f;
  --color-info: #007bff;
  --color-info-dark: #0056b3;
  --color-light-bg: #f9f9f9;
  --color-text: #333;
  --font-family-base:
    -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu, Cantarell,
    'Helvetica Neue', sans-serif;
  --max-width: 1200px;
  --spacing: 16px;
  --border-radius: 8px;
  --breakpoint-mobile: 600px;
  --difficulty-easy-color: #ecfdf5;
  --difficulty-medium-color: #fef9c3;
  --difficulty-hard-color: #fee2e2;
}

#app {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html,
body {
  position: relative;
  width: 100%;
  height: 100%;
}

body {
  color: var(--color-text);
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: var(--font-family-base);
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing);
}

h1,
h2,
h3 {
  font-weight: 600;
  line-height: 1.2;
  margin-top: 0;
}

a {
  color: rgb(0, 100, 200);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

a:visited {
  color: rgb(0, 80, 160);
}

label {
  display: block;
}

input,
button,
select,
textarea {
  font-family: inherit;
  font-size: inherit;
  -webkit-padding: 0.4em 0;
  padding: 0.4em;
  margin: 0 0 0.5em 0;
  box-sizing: border-box;
  border: 1px solid #ccc;
  border-radius: 2px;
}

input:disabled {
  color: #ccc;
}

button {
  color: var(--color-text);
  background-color: var(--color-light-bg);
  outline: none;
}

button:disabled {
  color: #999;
}

button:not(:disabled):active {
  background-color: #ddd;
}

button:focus {
  border-color: #666;
}

/* Difficulty-based question card colors */
.question-card.difficulty-easy .card-front,
.question-card.difficulty-easy .card-back {
  background-color: var(--difficulty-easy-color);
}

.question-card.difficulty-medium .card-front,
.question-card.difficulty-medium .card-back {
  background-color: var(--difficulty-medium-color);
}

.question-card.difficulty-hard .card-front,
.question-card.difficulty-hard .card-back {
  background-color: var(--difficulty-hard-color);
}