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

:root {
    --hue: 223;
    --bg: hsl(var(--hue), 90%, 90%);
    --fg: hsl(var(--hue), 90%, 10%);
    --primary: hsl(var(--hue), 90%, 50%);
    --trans-dur: 0.3s;
    font-size: calc(16px + (32 - 16) * (100vw - 320px) / (2560 - 320));
}

body {
    background-color: var(--bg);
    color: var(--fg);
    display: flex;
    font: 1em/1.5 sans-serif;
    height: 100vh;
    transition:
        background-color var(--trans-dur),
        color var(--trans-dur);
}

.bike {
    display: block;
    margin: auto;
    width: 16em;
    height: auto;
}

.bike__body,
.bike__front,
.bike__handlebars,
.bike__pedals,
.bike__pedals-spin,
.bike__seat,
.bike__spokes,
.bike__spokes-spin,
.bike__tire {
    animation: bikeBody 3s ease-in-out infinite;
    stroke: var(--primary);
    transition: stroke var(--trans-dur);
}

.bike__front {
    animation-name: bikeFront;
}

.bike__handlebars {
    animation-name: bikeHandlebars;
}

.bike__pedals {
    animation-name: bikePedals;
}

.bike__pedals-spin {
    animation-name: bikePedalsSpin;
}

.bike__seat {
    animation-name: bikeSeat;
}

.bike__spokes,
.bike__tire {
    stroke: currentColor;
}

.bike__spokes {
    animation-name: bikeSpokes;
}

.bike__spokes-spin {
    animation-name: bikeSpokesSpin;
}

.bike__tire {
    animation-name: bikeTire;
}

/* Dark theme */
@media (prefers-color-scheme: dark) {
    :root {
        --bg: hsl(var(--hue), 90%, 10%);
        --fg: hsl(var(--hue), 90%, 90%);
    }
}

/* Animations */
@keyframes bikeBody {
    from {
        stroke-dashoffset: 79;
    }

    33%,
    67% {
        stroke-dashoffset: 0;
    }

    to {
        stroke-dashoffset: -79;
    }
}

@keyframes bikeFront {
    from {
        stroke-dashoffset: 19;
    }

    33%,
    67% {
        stroke-dashoffset: 0;
    }

    to {
        stroke-dashoffset: -19;
    }
}

@keyframes bikeHandlebars {
    from {
        stroke-dashoffset: 10;
    }

    33%,
    67% {
        stroke-dashoffset: 0;
    }

    to {
        stroke-dashoffset: -10;
    }
}

@keyframes bikePedals {
    from {
        animation-timing-function: ease-in;
        stroke-dashoffset: -25.133;
    }

    33%,
    67% {
        animation-timing-function: ease-out;
        stroke-dashoffset: -21.991;
    }

    to {
        stroke-dashoffset: -25.133;
    }
}

@keyframes bikePedalsSpin {
    from {
        transform: rotate(0.1875turn);
    }

    to {
        transform: rotate(3.1875turn);
    }
}

@keyframes bikeSeat {
    from {
        stroke-dashoffset: 5;
    }

    33%,
    67% {
        stroke-dashoffset: 0;
    }

    to {
        stroke-dashoffset: -5;
    }
}

@keyframes bikeSpokes {
    from {
        animation-timing-function: ease-in;
        stroke-dashoffset: -31.416;
    }

    33%,
    67% {
        animation-timing-function: ease-out;
        stroke-dashoffset: -23.562;
    }

    to {
        stroke-dashoffset: -31.416;
    }
}

@keyframes bikeSpokesSpin {
    from {
        transform: rotate(0);
    }

    to {
        transform: rotate(3turn);
    }
}

@keyframes bikeTire {
    from {
        animation-timing-function: ease-in;
        stroke-dashoffset: 56.549;
        transform: rotate(0);
    }

    33% {
        stroke-dashoffset: 0;
        transform: rotate(0.33turn);
    }

    67% {
        animation-timing-function: ease-out;
        stroke-dashoffset: 0;
        transform: rotate(0.67turn);
    }

    to {
        stroke-dashoffset: -56.549;
        transform: rotate(1turn);
    }
}