* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    -webkit-tap-highlight-color: transparent;
}

body {
    background-color: #0e1621;
    color: #fff;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    overflow: hidden;
}

/* Khung hiển thị chuẩn di động (Mobile Frame) */
.app-container {
    width: 100%;
    max-width: 480px;
    height: 100%;
    max-height: 100vh;
    background: #17212b;
    display: flex;
    flex-direction: column;
    position: relative;
    box-shadow: 0 0 25px rgba(0,0,0,0.6);
    overflow: hidden;
}

@media (min-width: 481px) {
    .app-container {
        height: 90vh;
        border-radius: 16px;
        border: 1px solid #242f3d;
    }
}