body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background: #f4f6f8;
}

header {
    background: #2c3e50;
    color: white;
    padding: 15px;
    text-align: center;
}

.container {
    width: 95%;
    max-width: 1000px;
    margin: 20px auto;
    background: white;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 0 8px rgba(0,0,0,0.1);
}

input, select, button {
    padding: 10px;
    margin: 5px 0;
    width: 100%;
    box-sizing: border-box;
    border-radius: 5px;
    border: 1px solid #ccc;
}

button {
    background: #3498db;
    color: white;
    border: none;
    cursor: pointer;
}

button:hover {
    background: #2980b9;
}

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

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

th, td {
    padding: 10px;
    text-align: left;
}

th {
    background: #3498db;
    color: white;
}

.valid {color: green; font-weight: bold;}
.invalid {color: red; font-weight: bold;}