/* General Styles */
body {
  font-family: 'Roboto', sans-serif; /* Modern font */
  margin: 0;
  background: #f4f4f4;
  color: #333;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
}

.container {
  background: #fff;
  padding: 30px;
  border-radius: 10px;
  width: 85%;
  
  margin-top: 20px;
}


h1 {
    font-size: 2.5rem;
    color: #343a40; /* Màu xám đậm */
    text-align: center;
    margin-bottom: 2rem;
}

h2 {
    color: #333;
}

#problem {
 font-size: 1.2em;
    font-weight: bold;
    color: #2196F3; /* Màu xanh dương */
    padding: 10px 20px;   /* Thêm khoảng đệm */
    border-radius: 5px;   /* Bo tròn góc */
    background-color: #f0f0f0; /* Màu nền xám nhạt */
    border: 1px solid #ddd; /* Đường viền */
    margin-bottom: 20px; /* Khoảng cách với phần tử bên dưới */
    text-align: center; /* Căn giữa chữ */
}


/* Typography */
h1 {
    font-size: 2.5rem;
    color: #343a40; /* Màu xám đậm */
    text-align: center;
    margin-bottom: 2rem;
}
p {
  line-height: 1.6;
  margin-bottom: 15px;
}

/* Problem Area */
#problem-container {
  margin-bottom: 30px;
}

#problem-statement {
  font-size: 1.2em;
  margin-bottom: 20px;
}

/* Input Area */
#input-container {
  display: flex;
  justify-content: center;
  align-items: center;
}

input[type="number"] {
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 5px;
  width: 100px;
  margin: 0 10px;
  font-size: 1em;
  text-align: center;
}

/* Button Styles */
button {
  background-color: #007bff; /* Blue */
  color: #fff;
  padding: 12px 20px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  font-size: 1em;
  transition: background-color 0.3s ease;
}

button:hover {
  background-color: #0056b3;
}

/* Result Area */
#result {
  margin-top: 20px;
  font-size: 1.2em;
  text-align: center;
}

.correct {
  color: #28a745; /* Green */
}

.incorrect {
  color: #dc3545; /* Red */
}

/* History Area */
#history-container {
  margin-top: 30px;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 20px;
}

th, td {
  border: 1px solid #ddd;
  padding: 10px;
  text-align: left;
}

th {
  background-color: #f0f0f0;
}

/* Responsive Design */
@media (max-width: 768px) {
  .container {
    width: 95%;
    padding: 20px;
  }

  input[type="number"] {
    width: 80px;
  }
}
table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    font-size: 16px;
    text-align: left;
}

table th, table td {
    padding: 12px 15px;
    border: 1px solid #ddd;
}

table th {
    background-color: #f2f2f2;
    color: #333;
}

table tr:nth-child(even) {
    background-color: #f9f9f9;
}

table tr:hover {
    background-color: #f1f1f1;
}

table td {
    vertical-align: top;
}