Awesome CSS effects

Walk-throughs of how to create a bunch of awesome CSS effects paired with pleasant background music.
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(dimgray, silver, silver, dimgray);
    }
    
    .card {
        width: 400px;
        background: linear-gradient(#333, dimgray);
        color: white;
        box-sizing: border-box;
        padding: 20px;
    html, body {
        width: 100%;
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(to top left, white, dimgray);
        font-size: 7px;
    }
    
    .books {
        display: flex;
        width: calc(12rem * 3 + 3rem * 2);
        justify-content: space-between;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: brown;
    }
    
    .coffee {
        display: flex;
        flex-direction: column;
        align-items: center;
        height: calc(9em + 1em + 2em);
        position: relative;
张偶10:4918 days ago
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(brown, sandybrown);
    }
    
    .text {
        font-size: 5em;
        font-family: "arial black";
        position: relative;
        color: transparent;
    }
    html,
    body,
    .circle {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    :root {
        --innerRadius: 2em;
    }
    
    html,
    body,
    .circle {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .circle,
    .circle::before,
    .circle::after {
        border-width: 0.4em;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
        color: silver;
    }
    
    .box {
        width: 9em;
        height: 3em;
        text-align: center;
        line-height: 3em;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(to bottom, teal, aqua);
    }
    
    .battery {
        width: 6em;
        height: 3em;
        color: midnightblue;
        border: 0.5em solid currentColor;
        border-radius: 0.2em;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .box {
        display: flex;
    }
    
    .box .inner {
        width: 200px;
        height: 100px;
    html,
    body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    :root {
        --color1: deepskyblue;
        --color2: steelblue;
        --color3: royalblue;
        --color4: dodgerblue;
    }
    html,
    body,
    .checkbox,
    .checkbox .inner,
    .checkbox .inner .toggle {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .checkbox {
        width: 10em;
        height: 5em;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: skyblue;
    }
    
    .box {
        background: linear-gradient(to right, gold, darkorange);
        color: white;
        --width: 250px;
        --height: calc(var(--width) / 3);
        width: var(--width);
    html,
    body,
    .box .content {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .box {
        width: 300px;
        height: 300px;
        background: linear-gradient(
            -45deg,
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .loader {
        width: 150px;
        height: 150px;
        position: relative;
    }
    
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .box {
        width: 200px;
        height: 60px;
        border: 2px solid black;
        text-align: center;
        font-size: 30px;
        line-height: 60px;
    html,
    body,
    .box {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    body {
        background-color: #222;
    }
    
    .box {
    html,
    body,
    .loader {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .loader {
        width: 10em;
        height: 10em;
        position: relative;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(gray, silver);
    }
    
    .four-zero-four p {
        width: 10em;
        height: 10em;
        display: inline-block;
        font-size: 12px;
        margin: 0.5em;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .menu {
        padding: 0;
    }
    
    .menu li {
        color: transparent;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(silver, white);
    }
    
    .heart {
        display: grid;
        grid-gap: 2px;
        grid-template-columns: repeat(9, 1fr);
    }
    
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: darkcyan;
    }
    
    h1 {
        color: gold;
        text-align: center;
        position: relative;
    }
    
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .rainbow {
        color: transparent;
        font-size: 150px;
        font-family: sans-serif;
        font-weight: bold;
        text-transform: uppercase;
    html, body {
        width: 100%;
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(to right bottom, gold, chocolate);
    }
    
    :root {
        --x: 3em;
        --y: 1.5em;
    }
    
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(antiquewhite, navajowhite);
    }
    
    .sea {
        width: 300px;
        height: 300px;
        background-color: whitesmoke;
        background-image: linear-gradient(
            darkblue,
张偶8:526 days ago
    html,
    body,
    .loader {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .loader {
        width: 200px;
        height: 200px;
        position: relative;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: linear-gradient(cadetblue, darkcyan);
    }
    
    nav {
        width: 300px;
        height: 300px;
        background: lemonchiffon;
        box-shadow: 0 5px 30px rgba(0, 0, 0, 0.2);
        border-radius: 10px;
    html,
    body,
    .bows {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background: black;
    }
    
    .rainbow {
        width: 20em;
        height: 10em;
        border: 1px dashed white;/* just assistant, will be removed finally */
张偶8:593 days ago
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
        background-color: black;
    }
    
    .penrose {
        width: 20em;
        height: 20em;
        position: relative;
        font-size: 12px;
        top: -1em;
    html, body {
        height: 100%;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .frame {
        background: whitesmoke;
        width: 100vmin;
        height: 100vmin;
        position: relative;
        perspective: 40vmin;
    }