body {
    margin: 0;
    display: flex;
    flex-direction: column;
    height: 100vh;
    font-family: sans-serif;
}
header {
    display: flex;
    justify-content: space-between;
    padding: 10px 20px;
    background: #f4f4f4;
    border-bottom: 1px solid #ddd;
}
main {
    display: flex;
    flex: 1;
}
textarea, #preview {
    flex: 1;
    padding: 20px;
    overflow-y: auto;
    border: none;
    box-sizing: border-box;
}
textarea {
    border-right: 1px solid #eee;
    resize: none;
    outline: none;
    font-family: monospace;
}
#preview {
    background: #fff;
}
#status {
    font-size: 0.8rem;
    color: #666;
}