CodePen Embed - CSS Cityscape

<body>
    <div class="background-buildings sky">
        <div></div>
        <div></div>
        <div class="bb1 building-wrap">
            <div class="bb1a bb1-window"></div>
            <div class="bb1b bb1-window"></div>
            <div class="bb1c bb1-window"></div>
            <div class="bb1d"></div>
        </div>
        <div class="bb2">
            <div class="bb2a"></div>
            <div class="bb2b"></div>
        </div>
        <div class="bb3"></div>
        <div></div>
        <div class="bb4 building-wrap">
            <div class="bb4a"></div>
            <div class="bb4b"></div>
            <div class="bb4c window-wrap">
                <div class="bb4-window"></div>
                <div class="bb4-window"></div>
                <div class="bb4-window"></div>
                <div class="bb4-window"></div>
            </div>
        </div>
        <div></div>
        <div></div>
    </div>
    <div class="foreground-buildings">
        <div></div>
        <div></div>
        <div class="fb1 building-wrap">
            <div class="fb1a"></div>
            <div class="fb1b"></div>
            <div class="fb1c"></div>
        </div>
        <div class="fb2">
            <div class="fb2a"></div>
            <div class="fb2b window-wrap">
                <div class="fb2-window"></div>
                <div class="fb2-window"></div>
                <div class="fb2-window"></div>
            </div>
        </div>
        <div></div>
        <div class="fb3 building-wrap">
            <div class="fb3a window-wrap">
                <div class="fb3-window"></div>
                <div class="fb3-window"></div>
                <div class="fb3-window"></div>
            </div>
            <div class="fb3b"></div>
            <div class="fb3a"></div>
            <div class="fb3b"></div>
        </div>
        <div class="fb4 building-wrap">
            <div class="fb4a"></div>
            <div class="fb4b">
                <div class="fb4-window"></div>
                <div class="fb4-window"></div>
                <div class="fb4-window"></div>
                <div class="fb4-window"></div>
                <div class="fb4-window"></div>
                <div class="fb4-window"></div>
            </div>
        </div>
        <div class="fb5"></div>
        <div class="fb6"></div>
        <div></div>
        <div></div>
    </div>
</body>

:root {
    --building-color1: #aa80ff;
    --building-color2: #66cc99;
    --building-color3: #cc6699;
    --building-color4: #538cc6;
    --window-color1: #bb99ff;
    --window-color2: #8cd9b3;
    --window-color3: #d98cb3;
    --window-color4: #8cb3d9;
}

* {
    box-sizing: border-box;
}

body {
    height: 100vh;
    margin: 0;
    overflow: hidden;
}

.background-buildings,
.foreground-buildings {
    display: flex;
    flex-direction: row;
    justify-content: space-evenly;
    align-items: flex-end;
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
}

.building-wrap {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.window-wrap {
    display: flex;
    align-items: center;
    justify-content: space-evenly;
}

.sky {
    background: radial-gradient(
        circle closest-corner at 15% 15%,
        #ffcf33 0%,
        #ffcf33 20%,
        #ffff66 21%,
        #bbeeff 100%
    );
}

/* BACKGROUND BUILDINGS - "bb" stands for "background building" */

.bb1 {
    width: 10%;
    height: 70%;
}

.bb1a {
    width: 70%;
}

.bb1b {
    width: 80%;
}

.bb1c {
    width: 90%;
}

.bb1d {
    width: 100%;
    height: 70%;
    background: linear-gradient(
        var(--building-color1) 50%,
        var(--window-color1)
    );
}

.bb1-window {
    height: 10%;
    background: linear-gradient(
        var(--building-color1),
        var(--window-color1)
        );
}

.bb2 {
    width: 10%;
    height: 50%;
}

.bb2a {
    border-bottom: 5vh solid var(--building-color2);
    border-left: 5vw solid transparent;
    border-right: 5vw solid transparent;
}

.bb2b {
    width: 100%;
    height: 100%;
    background: repeating-linear-gradient(
        var(--building-color2) 0%,
        var(--building-color2) 6%,
        var(--window-color2) 6%,
        var(--window-color2) 9%
    );
}

.bb3 {
    width: 10%;
    height: 55%;
    background: repeating-linear-gradient(
        90deg,
        var(--building-color3),
        var(--building-color3),
        var(--window-color3) 15%
    );
}

.bb4 {
    width: 11%;
    height: 58%;
}

.bb4a {
    width: 3%;
    height: 10%;
    background-color: var(--building-color4);
}

.bb4b {
    width: 80%;
    height: 5%;
    background-color: var(--building-color4);
}

.bb4c {
    width: 100%;
    height: 85%;
    background-color: var(--building-color4);
}

.bb4-window {
    width: 18%;
    height: 90%;
    background-color: var(--window-color4);
}

/* FOREGROUND BUILDINGS - "fb" stands for "foreground building" */

.fb1 {
    width: 10%;
    height: 60%;
}

.fb1a {
    border-bottom: 7vh solid var(--building-color4);
    border-left: 2vw solid transparent;
    border-right: 2vw solid transparent;
}

.fb1b {
    width: 60%;
    height: 10%;
    background-color: var(--building-color4);
}

.fb1c {
    width: 100%;
    height: 80%;
    background: repeating-linear-gradient(
        90deg,
        var(--building-color4) 0%,
        var(--building-color4) 10%,
        transparent 10%,
        transparent 15%
    ),
    repeating-linear-gradient(
        var(--building-color4) 0%,
        var(--building-color4) 10%,
        var(--window-color4) 10%,
        var(--window-color4) 90%
    );
}

.fb2 {
    width: 10%;
    height: 40%;
}

.fb2a {
    width: 100%;
    border-bottom: 10vh solid var(--building-color3);
    border-left: 1vw solid transparent;
    border-right: 1vw solid transparent;
}

.fb2b {
    width: 100%;
    height: 75%;
    background-color: var(--building-color3);
}

.fb2-window {
    width: 22%;
    height: 100%;
    background-color: var(--window-color3);
}

.fb3 {
    width: 10%;
    height: 35%;
}

.fb3a {
    width: 80%;
    height: 15%;
    background-color: var(--building-color1);
}

.fb3b {
    width: 100%;
    height: 35%;
    background-color: var(--building-color1);
}

.fb3-window {
    width: 25%;
    height: 80%;
    background-color: var(--window-color1);
}

.fb4 {
    width: 8%;
    height: 45%;
    position: relative;
    left: 10%;
}

.fb4a {
    border-top: 5vh solid transparent;
    border-left: 8vw solid var(--building-color1);
}

.fb4b {
    width: 100%;
    height: 89%;
    background-color: var(--building-color1);
    display: flex;
    flex-wrap: wrap;
}

.fb4-window {
    width: 30%;
    height: 10%;
    border-radius: 50%;
    background-color: var(--window-color1);
    margin: 10%;
}

.fb5 {
    width: 10%;
    height: 33%;
    background: repeating-linear-gradient(
        var(--building-color2) 0%,
        var(--building-color2) 5%,
        transparent 5%,
        transparent 10%
    ),
    repeating-linear-gradient(
        90deg,
        var(--building-color2) 0%,
        var(--building-color2) 12%,
        var(--window-color2) 12%,
        var(--window-color2) 44%
    );
    position: relative;
    right: 10%;
}

.fb6 {
    width: 9%;
    height: 38%;
    background: repeating-linear-gradient(
        90deg,
        var(--building-color3) 0%,
        var(--building-color3) 10%,
        transparent 10%,
        transparent 30%
        ),
        repeating-linear-gradient(
        var(--building-color3) 0%,
        var(--building-color3) 10%,
        var(--window-color3) 10%,
        var(--window-color3) 30%
    );
}

@media (max-width: 1000px) {
    :root {
        --building-color1: #000;
        --building-color2: #000;
        --building-color3: #000;
        --building-color4: #000;
        --window-color1: #777;
        --window-color2: #777;
        --window-color3: #777;
        --window-color4: #777;
    }

    .sky {
        background: radial-gradient(
            circle closest-corner at 15% 15%,
            #ccc 0%,
            #ccc 20%,
            #445 21%,
            #223 100%
        );
    }   
}

This Pen is owned by Elliot Hill on CodePen.

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