body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f5f5f5;
    margin: 0;
    padding: 0;
    color: #333;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

.login-container {
    max-width: 400px;
    margin: 100px auto;
    padding: 30px;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.dashboard-container {
    margin-top: 20px;
}

h1 {
    color: #2c3e50;
    margin-bottom: 30px;
    text-align: center;
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.invalid-cell {
    color: red;
}

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 12px 15px;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

th {
    background-color: #f2f2f2;
    position: sticky;
    top: 0;
}

tr:hover {
    background-color: #f5f5f5;
}

.action-buttons {
    display: flex;
    justify-content: flex-end;
    margin-top: 20px;
}

.status-message {
    margin-top: 20px;
    padding: 10px;
    border-radius: 4px;
}

.success {
    background-color: #d4edda;
    color: #155724;
}

.error {
    background-color: #f8d7da;
    color: #721c24;
}

.loading {
    background-color: #e2e3e5;
    color: #383d41;
}

.logo {
    max-width: 200px;
    margin: 0 auto 20px;
    display: block;
}

.tabs {
    display: flex;
    margin-bottom: 20px;
}

.tab-btn {
    background-color: #e0e0e0;
    color: #333;
    padding: 10px 20px;
    margin-right: 5px;
    cursor: pointer;
    border-radius: 4px 4px 0 0;
    border: none;
    font-size: 16px;
    transition: background-color 0.3s;
}

.tab-btn.active {
    background-color: #4CAF50;
    color: white;
}

.sheet-container {
    display: none;
    overflow-x: auto;
    margin-bottom: 30px;
    border: 1px solid #ddd;
    border-radius: 4px;
    max-height: 600px;
    overflow-y: auto;
}

.sheet-container.active {
    display: block;
}

.logout-btn {
    background-color: #f44336;
    margin-left: 10px;
}

.logout-btn:hover {
    background-color: #d32f2f;
}

button {
    background-color: #4CAF50;
    color: white;
    padding: 12px 20px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 16px;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #45a049;
}