*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body {
    font-family: Arial;
    display: flex;
    min-height: 100vh;/*1hv=1/100 chieu cao view*/
    background: #f4f4f4;
}
.leftbar {
    width: 250px;
    background-color: #2c3e50;
    color: white;
    padding: 1rem;
}
.leftbar h2{
    margin-bottom: 2rem;
}
.leftbar a{
    display: block;
    color: white;
    text-decoration: none;
    margin-bottom: 1rem;
}
.leftbar a:hover {
    text-decoration: underline;
}
.main {
    flex-grow: 1;
    padding: 2rem;
}
.cards {
    display: grid;
    grid-template-columns: repeat(3,1fr);/*fraction*/
    gap: 1rem;
}
.card {
    background: white;
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}
.card h3{
    margin-bottom: 0.5rem;/*8px*/
}
tbale {
    width: 100%;
    border-collapse: collapse;
    margin-top: 2rem;

}
table th, table td {
    padding: 0.75rem;
    text-align: left;
    border-bottom: 1px solid #ccc;
}
table th {
    background-color: #ecf0f1;
}