body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    font-family: Arial, sans-serif;
    background: #f2f2f2;
    display: flex;
    flex-direction: column;
}

header {
    height: 60px;
    background: white;
    display: flex;
    align-items: center;
    padding: 0 20px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    font-size: 20px;
    font-weight: bold;
}

/* LOGIN */
.app-screen {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}