/* Reset & Base */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Segoe UI", Arial, sans-serif;
  background: #f9f9f9;
  color: #333;
  line-height: 1.6;
}

/* Header */
header {
  background: #004080;
  color: white;
  padding: 1rem;
  text-align: center;
}

header h1 {
  font-size: 1.8rem;
}

header p {
  font-size: 1rem;
  margin-top: 0.3rem;
}

.back {
  display: inline-block;
  margin-top: 0.5rem;
  color: #ffdd57;
  text-decoration: none;
  font-size: 0.9rem;
}

/* Grid for Homepage */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1rem;
  padding: 1.5rem;
}

/* Section Cards */
.card {
  background: white;
  padding: 2rem 1rem;
  text-align: center;
  border-radius: 10px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.1);
  text-decoration: none;
  font-size: 1.2rem;
  color: #004080;
  transition: transform 0.2s, background 0.2s;
}

.card:hover {
  transform: translateY(-4px);
  background: #f0f7ff;
}

/* Chapters List */
ul.chapters {
  list-style: none;
  padding: 1rem;
}

ul.chapters li {
  background: white;
  margin: 0.6rem 0;
  padding: 1rem;
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.08);
  display: flex;
  flex-direction: column;
}

ul.chapters li span {
  font-weight: bold;
  margin-bottom: 0.5rem;
}

.links a {
  margin-right: 1rem;
  color: #004080;
  text-decoration: none;
  font-size: 0.95rem;
}

/* Question Box */
#question-box {
  margin-top: 1rem;
  padding: 1rem;
  background: #fff;
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
}

/* Buttons */
button {
  padding: 0.6rem 1.2rem;
  border: none;
  background: #004080;
  color: white;
  border-radius: 6px;
  cursor: pointer;
  font-size: 1rem;
}

button:hover {
  background: #003366;
}

/* Responsive Breakpoints */
@media (max-width: 900px) {
  header h1 {
    font-size: 1.5rem;
  }
  .card {
    font-size: 1rem;
    padding: 1.5rem 1rem;
  }
  .solution-img {
  max-width: 50%;
  height: auto;
  margin-top: 0.8rem;
  border-radius: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
}
}

@media (max-width: 600px) {
  header h1 {
    font-size: 1.3rem;
  }
  header p {
    font-size: 0.9rem;
  }
  .grid {
    grid-template-columns: 1fr 1fr;
    gap: 0.8rem;
    padding: 1rem;
  }
  .card {
    font-size: 1rem;
    padding: 1rem;
  }
  ul.chapters li {
    font-size: 0.95rem;
  }
  .solution-img {
  max-width: 70%;
  height: auto;
  margin-top: 0.8rem;
  border-radius: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
}
}

@media (max-width: 400px) {
  .grid {
    grid-template-columns: 1fr;
  }
  .card {
    font-size: 1rem;
  }
  .solution-img {
  max-width: 100%;
  height: auto;
  margin-top: 0.8rem;
  border-radius: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
}
}
.solution-img {
  max-width: 50%;
  height: auto;
  margin-top: 0.8rem;
  border-radius: 6px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
}
.show-solution {
  margin-left:10px;
  cursor: pointer;
 
}
.question-box {
      background: #fff;
      padding: 1rem;
      margin: 1rem 0;
      border-radius: 8px;
      box-shadow: 0 1px 4px rgba(0,0,0,0.1);
    }
.question-box input {
      padding: 0.5rem;
      width: 180px;
      margin-right: 0.5rem;
      border: 1px solid #ccc;
      border-radius: 6px;
    }
.correct { color: green; font-weight: bold; margin-left: 0.5rem; }
.wrong { color: red; font-weight: bold; margin-left: 0.5rem; }
/* MathJax Styling */
.MathJax, 
mjx-container[jax="CHTML"] {
  font-size: 1.2em; /* базовый размер формул */
  line-height: 1.4;
}

/* Более крупные формулы на маленьких экранах */
@media (max-width: 900px) {
  .MathJax,
  mjx-container[jax="CHTML"] {
    font-size: 1.3em;
  }
}

@media (max-width: 600px) {
  .MathJax,
  mjx-container[jax="CHTML"] {
    font-size: 1.4em;
  }
}

@media (max-width: 400px) {
  .MathJax,
  mjx-container[jax="CHTML"] {
    font-size: 1.5em;
  }
}