* {
    box-sizing: border-box;
}

body {
    font-family: Arial, sans-serif;
    margin: 0;
    background: #f5f5f5;
}

header {
    padding: 20px;
    background: #222;
    color: white;
}

    header h1 {
        margin: 0 0 15px;
    }

nav button {
    padding: 10px 15px;
    margin-right: 5px;
    cursor: pointer;
}

main {
    padding: 20px;
}

section {
    background: white;
    padding: 20px;
    border-radius: 5px;
}

.hidden {
    display: none;
}

input,
select {
    padding: 10px;
    margin: 5px;
}

button {
    padding: 10px 15px;
    cursor: pointer;
}

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

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

th {
    background: #eee;
}