* {
 margin: 0;
 padding: 0;
 box-sizing: border-box;
}

body {
 font-family: 'Roboto', Arial, sans-serif; /* Thêm font Roboto hỗ trợ tiếng Việt */
 line-height: 1.6;
}

header {
 background: #333;
 color: #fff;
 padding: 10px 0;
}

nav ul {
 list-style: none;
 display: flex;
 justify-content: center;
}

nav ul li {
 margin: 0 20px;
}

nav ul li a {
 color: #fff;
 text-decoration: none;
}

.container {
 width: 80%;
 margin: 20px auto;
}

h2 {
 margin-bottom: 20px;
}

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

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

table th {
 background: #f4f4f4;
}

.btn {
 display: inline-block;
 padding: 8px 16px;
 background: #333;
 color: #fff;
 text-decoration: none;
 border-radius: 4px;
}

.btn-danger {
 background: #e00;
}

form {
 display: flex;
 flex-direction: column;
 gap: 10px;
 max-width: 500px;
}

input, select, button, textarea {
 padding: 10px;
 font-size: 16px;
}

textarea {
 height: 100px;
}

button {
 background: #333;
 color: #fff;
 border: none;
 cursor: pointer;
}

button:hover {
 background: #555;
}

.error {
 color: red;
}

.login-container {
 width: 300px;
 margin: 100px auto;
 text-align: center;
}

.product-row {
 display: flex;
 gap: 10px;
 margin-bottom: 10px;
}

.invoice {
 border: 1px solid #ddd;
 padding: 20px;
 max-width: 600px;
 margin: 20px auto;
 background: #fff;
}

.invoice-header, .invoice-footer {
 text-align: center;
 margin-bottom: 20px;
}

@media print {
 .no-print {
 display: none;
 }
 .invoice {
 border: none;
 margin: 0;
 }
}

footer {
 text-align: center;
 padding: 10px;
 background: #333;
 color: #fff;
 position: fixed;
 bottom: 0;
 width: 100%;
}

/* Thêm font từ Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@400;700&display=swap');