styles.css

* {
    box-sizing: border-box;
}

header {
    width: 800px;
}

h1 {
    width: 100%;
    text-align: center;
    background-color: aqua;
    padding: 20px 0;
    border: 3px solid #333;
}

form > * {
    display: block;
}

form {
    width: 800px;
    background-color: aqua;
    padding: 20px;
}

label,
input,
textarea {
    margin-bottom: 10px;
}

textarea {
    width: 700px;
    resize: none;
}

#input-submit {
    width: 100px;
    height: 50px;
}

.tweet-container {
    margin-top: 30px;
    width: 800px;
    background-color: aqua;
}

.checkBtn-container {
    width: 100%;
    padding: 20px;
    background-color: bisque;
}

.btn_checkNewTweet {
    padding: 10px 20px;
}

.tweet-listgroup {
    padding-inline-start: 0;
    padding: 0 20px;
    list-style-type: none;
    padding-bottom: 30px;
}

.tweet {
    border-bottom: 1px solid #000;
}

.tweet-info {
    display: grid;
    grid-template-columns: 1fr auto auto;
    column-gap: 20px;
}