styles.css

html {
    box-sizing: border-box;
}

*, *::before, *::after {
    box-sizing: inherit;
    margin: 0;
    padding: 0;
}

body {
    font-family:
        -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans,
        Ubuntu, Cantarell, 'Helvetica Neue', sans-serif;
    line-height: 1.4;
}

form {
    width: 100%;
    display: flex;
    justify-content: space-between;
    flex-direction: column;
    align-items: center;
}

input[type="text"] {
    width: 100%;
    padding: 10px;
    border-radius: 4px;
    border: 3px solid #666;
    margin-top: 4px;
}

.container {
    width: 100%;
    max-width: 500px;
    margin: 0 auto;
    padding-left: 10px;
    padding-right: 10px;
    color: #333;
    height: 90vh;
    margin-top: 5vh;
    margin-bottom: 5vh;
    overflow-y: auto;
}

.app-title {
    text-align: center;
    margin-bottom: 20px;
    font-size: 80px;
    opacity: 0.8;
}

.todo-list {
    list-style: none;
    margin-bottom: 20px;
}

.todo-list:empty {
    display: none;
}