モーダルウィンドウ（テキスト・ボタン）

デモ

See the Pen modal2 by logsuke (@design-list) on CodePen.

コード

<!-- Boxicons headタグ内へ -->
    <link href='https://unpkg.com/boxicons@2.1.2/css/boxicons.min.css' rel='stylesheet'>

    <main>
        <div id="overlay">
        </div>

        <div id="modal">
            <div class="modal-header">
                <h3>modal</h3>
                <i id="close" class="bx bx-x"></i>
            </div>
            <div class="modal-content">
                Lorem ipsum dolor sit amet consectetur adipisicing elit. Mollitia doloribus commodi assumenda a
                voluptate culpa sunt minus nemo fugiat explicabo!
            </div>
            <div class="modal-footer">
                <button class="ok">ok!</button>
                <button class="cancel">cancel</button>
            </div>
        </div>
        <section id="section1" class="section">

            <button id="button" class="button">modal</button>
        </section>
    </main>

/*=== Base ===*/

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box
}

:root {
    --nav-height: 8rem;
    --max-width: 1024px;
    --container-padding: 0 4rem;
    --gap: 2rem;
    --bg-color: rgb(240, 240, 240);
    --first-color: rgb(172, 245, 255);
}


/*=== Font ratio ===*/

html {
    scroll-behavior: smooth;
    font-size: 62.5%;
}

body {
    font-size: 1.6rem;
}

ul {
    list-style: none;
}

a {
    text-decoration: none;
}

.section {
    width: var(--max-width);
    margin: 0 auto;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 10rem;
}

/* tool tip */

.button {
    width: 150px;
    height: 50px;
    padding: .5rem 1rem;
    background: var(--first-color);
    border: none;
    font-size: 2rem;
    border-radius: .5rem;
    cursor: pointer;
    position: relative;
}

/* modal */

#overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(39, 39, 39, 0.664);
    z-index: 80;
    pointer-events: none;
    user-select: none;
    opacity: 0;
    transition: opacity .2s;
}

#overlay.show {
    opacity: 1;
    pointer-events: auto;
    user-select: auto;
}

#modal {
    width: 600px;
    max-width: 80%;
    max-height: 80%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: #fff;
    z-index: 100;
    border-radius: 1rem;
    pointer-events: none;
    user-select: none;
    opacity: 0;
    transition: opacity .2s;
}

#modal.show {
    opacity: 1;
    pointer-events: auto;
    user-select: auto;
}

#modal .modal-header {
    padding: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid #ccc;
}

#modal .modal-header i {
    padding: 1rem;
    background: #ccc;
    cursor: pointer;
}

#modal .modal-content {
    padding: 2rem;
}

#modal .modal-footer {
    padding: 2rem;
    border-top: 1px solid #ccc;
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
}

#modal .modal-footer button {
    padding: .5rem 1rem;
    border: none;
    font-size: 2rem;
    letter-spacing: .05rem;
    cursor: pointer;
}

#modal .modal-footer .ok {
    background: rgb(247, 139, 139);
    color: #fff;
}

#modal .modal-footer .cancel {
    background: #ccc;
    color: #fff;
}

const button = document.getElementById('button'),
    overlay = document.getElementById('overlay'),
    modal = document.getElementById('modal'),
    close = document.getElementById('close')

button.addEventListener('click', function() {
    modal.classList.add('show')
    overlay.classList.add('show')
})

close.addEventListener('click', function() {
    modal.classList.remove('show')
    overlay.classList.remove('show')
})