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HTML

              
                div(class='shopping-cart')
  div(class='bag')
    div(class='front')
      div(class='inner')
      canvas(width='240px' height='240px' data-x='0' data-y='-1280' data-mass='.8' data-damping='.8')
    div(class='back')
  div(class='count')
    div
      span(class='current') 0
  
a(class='minus' href='')
a(class='plus' href='')

a(class='dribbble' href='https://dribbble.com/shots/6808801-Shopping-Cart-Animation' target='_blank')
  img(src='https://cdn.dribbble.com/assets/dribbble-ball-mark-2bd45f09c2fb58dbbfb44766d5d1d07c5a12972d602ef8b32204d28fa3dda554.svg')
              
            
!

CSS

              
                .shopping-cart {
    --stroke: #242836;
    --stroke-light: #3F4656;
    --background: #FFF;
    --inner: #EEF4FF;
    --count-background: #275EFE;
    position: relative;
    // For demo
    zoom: 2;
    .bag {
        perspective: 64px;
        position: relative;
        transform-origin: 50% 100%;
        .front,
        .back,
        .inner {
            --x: 0;
            --y: 0;
            --z: 0;
            --r: 24deg;
            --s: 1;
            --sx: 1;
            width: 32px;
            position: relative;
            backface-visibility: hidden;
            transition: transform .5s ease, clip-path .7s ease;
            transform-origin: 50% 100%;
            border-radius: 2px;
            transform: translate3d(var(--x), var(--y), var(--z)) rotateX(var(--r)) scaleY(var(--s)) scaleX(var(--sx));
        }
        .front,
        .back {
            background: var(--background);
            border: 2px solid var(--stroke);
        }
        .front,
        .inner {
            &:before {
                content: '';
                position: absolute;
            }
        }
        .front {
            --z: 1px;
            z-index: 3;
            height: 32px;
            &:before {
                height: 2px;
                border-radius: 1px;
                bottom: 4px;
                left: 5px;
                right: 5px;
                background: var(--stroke-light);
            }
            canvas {
                width: 32px;
                height: 32px;
                position: absolute;
                left: 50%;
                top: 0;
                transform: translate(-50%, -52%);
            }
        }
        .back,
        .inner {
            position: absolute;
            top: 0;
        }
        .back {
            --r: 0deg;
            --y: 4px;
            --sx: .73;
            --s: .8;
            --z: -20px;
            height: 10px;
            left: 0;
        }
        .inner {
            --x: -50%;
            --y: -105%;
            --r: -130deg;
            --offset: 10px;
            height: 22px;
            left: 50%;
            background: var(--stroke);
            clip-path: polygon(6px 0, 26px 0, calc(32px - var(--offset)) 8px, 32px 22px, 0 22px, var(--offset) 8px);
            &:before {
                left: 0;
                top: 0;
                right: 0;
                bottom: 0;
                background: var(--inner);
                clip-path: polygon(6px 0, 26px 0, calc(32px - var(--offset)) 8px, 32px 22px, 0 22px, var(--offset) 8px);
                transform: scale(.76);
                transition: clip-path .7s ease;
            }
        }
    }
    .count {
        --o: 0;
        width: 16px;
        height: 16px;
        line-height: 16px;
        font-size: .5em;
        text-align: center;
        font-weight: 600;
        border-radius: 50%;
        background: var(--count-background);
        color: #fff;
        top: 100%;
        left: 50%;
        overflow: hidden;
        position: absolute;
        transform: translate(-50%, 8px);
        opacity: var(--o);
        transition: opacity .3s ease;
        div {
            span {
                display: block;
                width: 16px;
                height: 16px;
                line-height: 16px;
                &.before,
                &.after {
                    left: 0;
                    position: absolute;
                }
                &.before {
                    bottom: 100%;
                }
                &.after {
                    top: 100%;
                }
            }
        }
        &.moveUp {
            div {
                animation: moveUp .3s linear forwards;
            }
        }
        &.moveDown {
            div {
                animation: moveDown .3s linear forwards;
            }
        }
    }
    &:not(.open) {
        .bag {
            .inner {
                transition-delay: .01s;
            }
        }
    }
    &.open {
        .bag {
            .front {
                --r: -20deg;
                --s: .65;
            }
            .inner {
                --r: -64deg;
                --offset: 7px;
            }
            .back {
                --z: 8px;
            }
        }
        &.bounce {
            .bag {
                animation: bounce .3s linear;
            }
        }
    }
    &.counted {
        .count {
            --o: 1;
        }
    }
}

@keyframes bounce {
    36% {
        transform: scaleY(.9);
    }
}

@keyframes moveUp {
    100% {
        transform: translateY(-100%);
    }
}

@keyframes moveDown {
    100% {
        transform: translateY(100%);
    }
}

.plus,
.minus {
    --border: #CDD9ED;
    --icon: #99A3BA;
    --x: -120px;
    --s: 1;
    width: 24px;
    height: 24px;
    margin-left: -12px;
    position: absolute;
    left: 50%;
    top: 50%;
    border-radius: 50%;
    border: 1px solid var(--border);
    transition: transform .3s ease;
    transform: translate(var(--x), -50%) scale(var(--s));
    &:before,
    &:after {
        --r: 0deg;
        content: '';
        width: 14px;
        height: 2px;
        border-radius: 1px;
        margin: -1px 0 0 -7px;
        left: 50%;
        top: 50%;
        position: absolute;
        background: var(--icon);
        transform: rotate(var(--r)) scale(.7);
    }
    &:active {
        --s: .92;
    }
}

.plus {
    transform: translate(calc(var(--x) * -1), -50%) scale(var(--s));
    &:after {
        --r: 90deg;
    }
}

html {
    box-sizing: border-box;
    -webkit-font-smoothing: antialiased;
}

* {
    box-sizing: inherit;
    &:before,
    &:after {
        box-sizing: inherit;
    }
}

// Center & dribbble
body {
    min-height: 100vh;
    font-family: Roboto, Arial;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #fff;
    .dribbble {
        position: fixed;
        display: block;
        right: 20px;
        bottom: 20px;
        img {
            display: block;
            height: 28px;
        }
    }
}
              
            
!

JS

              
                var cart = $('.shopping-cart'),
    canvas = $('.shopping-cart canvas')[0],
    context = canvas.getContext('2d'),
    count = cart.find('.count'),
    current = 0,
    x = canvas.dataset.x,
    y = canvas.dataset.y;

$('.plus, .minus').on('click', e => {

    let minus = $(e.currentTarget).hasClass('minus');

    if(minus) {
        if(current == 0) {
            return false;
        }
        current--;
    } else {
        if(current >= 9) {
            return false;
        }
        current++;
    }

    let setY = current >= 1 && !cart.hasClass('open') ? y * -.7 : y;

    if(current == 0) {
        setY = -1280;
    }

    canvas.setAttribute('data-y', setY);

    cart.toggleClass('open', current >= 1);

    x = canvas.dataset.x;
    y = canvas.dataset.y;

    setTimeout(() => {
        setCount(current, minus);
    }, current == 1 && !minus ? 300 : 0);

    return false;

});

function setCount(value, minus) {
    cart.toggleClass('counted', value != 0);
    let moveClass = minus ? 'moveDown' : 'moveUp';
    count.children('div').append($('<span />').addClass(minus ? 'before' : 'after').text(value));
    count.addClass(moveClass);
    bounceCart();
    setTimeout(() => {
        count.find('.current').text(value);
        count.removeClass(moveClass);
        count.find('.before, .after').remove();
    }, 300);
}

function bounceCart() {
    canvas.setAttribute('data-y', y * 3);
    canvas.setAttribute('data-x', -200);
    setTimeout(() => {
        canvas.setAttribute('data-x', 200);
    }, 50);
    cart.addClass('bounce');
    setTimeout(() => {
        canvas.setAttribute('data-y', y);
        canvas.setAttribute('data-x', x);
        setTimeout(() => {
            cart.removeClass('bounce');
        }, 200);
    }, 100);
}

Math.lerp = (first, second, percentage) => {
    return first + (second - first) * percentage;
};

Math.clamp = (value, min, max) => {
    return value < min ? min : value > max ? max : value;
};

class App {
    constructor(
        window,
        canvas,
        context,
        updateHandler,
        drawHandler,
        frameRate = 60
    ) {
        this._window = window;
        this._canvas = canvas;
        this._context = context;
        this._updateHandler = updateHandler;
        this._drawHandler = drawHandler;
        this._frameRate = frameRate;
        this._lastTime = 0;
        this._currentTime = 0;
        this._deltaTime = 0;
        this._interval = 0;
        this.onMouseMoveHandler = (x, y) => {};
        this.onMouseDownHandler = (x, y) => {};
        this.start = this.start.bind(this);
        this._onMouseEventHandlerWrapper = this._onMouseEventHandlerWrapper.bind(this);
        this._onRequestAnimationFrame = this._onRequestAnimationFrame.bind(this);
    }
    start() {
        this._lastTime = new Date().getTime();
        this._currentTime = 0;
        this._deltaTime = 0;
        this._interval = 1000 / this._frameRate;
        this._canvas.addEventListener('mousemove', e => {
            this._onMouseEventHandlerWrapper(e, this.onMouseMoveHandler);
        }, false);
        this._canvas.addEventListener('mousedown', e => {
            this._onMouseEventHandlerWrapper(e, this.onMouseDownHandler);
        }, false);
        setInterval(() => {
            this._onRequestAnimationFrame();
        }, 30);
    }
    _onMouseEventHandlerWrapper(e, callback) {
        let element = this._canvas;
        let offsetX = 0;
        let offsetY = 0;
        if(element.offsetParent) {
            do {
                offsetX += element.offsetLeft;
                offsetY += element.offsetTop;
            } while ((element = element.offsetParent));
        }
        const x = e.pageX - offsetX;
        const y = e.pageY - offsetY;
        callback(x, y);
    }
    _onRequestAnimationFrame() {
        //this._window.requestAnimationFrame(this._onRequestAnimationFrame);
        this._currentTime = new Date().getTime();
        this._deltaTime = this._currentTime - this._lastTime;
        if(this._deltaTime > this._interval) {
            const dts = this._deltaTime * 0.001;
            this._updateHandler(dts);
            this._context.clearRect(0, 0, this._canvas.width, this._canvas.height);
            this._drawHandler(this._canvas, this._context, dts);
            this._lastTime = this._currentTime - this._deltaTime % this._interval;
        }
    }
}

class Vector2 {
    static zero() {
        return { x: 0, y: 0 };
    }
    static sub(a, b) {
        return { x: a.x - b.x, y: a.y - b.y };
    }
    static add(a, b) {
        return { x: a.x + b.x, y: a.y + b.y };
    }
    static mult(a, b) {
        return { x: a.x * b.x, y: a.y * b.y };
    }
    static scale(v, scaleFactor) {
        return { x: v.x * scaleFactor, y: v.y * scaleFactor };
    }
    static mag(v) {
        return Math.sqrt(v.x * v.x + v.y * v.y);
    }
    static normalized(v) {
        const mag = Vector2.mag(v);
        if(mag === 0) {
            return Vector2.zero();
        }
        return { x: v.x / mag, y: v.y / mag };
    }
}

class RopePoint {
    static integrate(point, gravity, dt, previousFrameDt) {
        point.velocity = Vector2.sub(point.pos, point.oldPos);
        point.oldPos = { ...point.pos };

        let timeCorrection = previousFrameDt != 0.0 ? dt / previousFrameDt : 0.0;

        let accel = Vector2.add(gravity, {
            x: 0,
            y: point.mass
        });

        const velCoef = timeCorrection * point.damping;
        const accelCoef = Math.pow(dt, 2);

        point.pos.x += point.velocity.x * velCoef + accel.x * accelCoef;
        point.pos.y += point.velocity.y * velCoef + accel.y * accelCoef;
    }
    static constrain(point) {
        if(point.next) {
            const delta = Vector2.sub(point.next.pos, point.pos);
            const len = Vector2.mag(delta);
            const diff = len - point.distanceToNextPoint;
            const normal = Vector2.normalized(delta);

            if(!point.isFixed) {
                point.pos.x += normal.x * diff * 0.25;
                point.pos.y += normal.y * diff * 0.25;
            }

            if(!point.next.isFixed) {
                point.next.pos.x -= normal.x * diff * 0.25;
                point.next.pos.y -= normal.y * diff * 0.25;
            }
        }
        if(point.prev) {
            const delta = Vector2.sub(point.prev.pos, point.pos);
            const len = Vector2.mag(delta);
            const diff = len - point.distanceToNextPoint;
            const normal = Vector2.normalized(delta);

            if(!point.isFixed) {
                point.pos.x += normal.x * diff * 0.25;
                point.pos.y += normal.y * diff * 0.25;
            }

            if(!point.prev.isFixed) {
                point.prev.pos.x -= normal.x * diff * 0.25;
                point.prev.pos.y -= normal.y * diff * 0.25;
            }
        }
    }
    constructor(initialPos, distanceToNextPoint) {
        this.pos = initialPos;
        this.distanceToNextPoint = distanceToNextPoint;
        this.isFixed = false;
        this.oldPos = { ...initialPos };
        this.velocity = Vector2.zero();
        this.mass = 1.0;
        this.damping = 1.0;
        this.prev = null;
        this.next = null;
    }
}

class Rope {
    static generate(start, end, resolution, canvas) {
        const delta = Vector2.sub(end, start);
        const len = Vector2.mag(delta);

        let points = [];
        const pointsLen = len / resolution;

        for(let i = 0; i < pointsLen; i++) {
            const percentage = i / (pointsLen - 1);

            const lerpX = Math.lerp(start.x, end.x, percentage);
            const lerpY = Math.lerp(start.y, end.y, percentage);

            points[i] = new RopePoint({
                x: lerpX,
                y: lerpY
            }, resolution);
            points[i].mass = canvas.dataset.mass;
            points[i].damping = canvas.dataset.damping;
        }

        for(let i = 0; i < pointsLen; i++) {
            const prev = i != 0 ? points[i - 1] : null;
            const curr = points[i];
            const next = i != pointsLen - 1 ? points[i + 1] : null;

            curr.prev = prev;
            curr.next = next;
        }

        points[0].isFixed = points[points.length - 1].isFixed = true;

        return points;
    }
    constructor(points, solverIterations) {
        this._points = points;
        this.update = this.update.bind(this);
        this._prevDelta = 0;
        this._solverIterations = solverIterations;

        this.getPoint = this.getPoint.bind(this);
    }
    getPoint(index) {
        return this._points[index];
    }
    update(canvas, dt) {
        if(document.hidden) {
            return;
        }
        for(let i = 1; i < this._points.length-1; i++) {
            let point = this._points[i];

            let accel = {
                x: canvas.dataset.x,
                y: canvas.dataset.y
            };

            RopePoint.integrate(point, accel, dt, this._prevDelta);
        }
        for(let iteration = 0; iteration < this._solverIterations; iteration++) {
            for(let i = 1; i < this._points.length-1; i++) {
                let point = this._points[i];
                RopePoint.constrain(point);
            }
        }
        this._prevDelta = dt;
    }
}

const args = {
    start: {
        x: canvas.width / 4,
        y: canvas.height / 2
    },
    end: {
        x: canvas.width - canvas.width / 4,
        y: canvas.height / 2
    },
    resolution: 4,
    mass: .8,
    damping: .8,
    solverIterations: 20,
    color: getComputedStyle(cart[0]).getPropertyValue('--stroke'),
    ropeSize: 14
};

const points = Rope.generate(
    args.start,
    args.end,
    args.resolution,
    canvas
);

let rope = new Rope(points, args.solverIterations);

const tick = dt => {
    rope.update(canvas, dt);
};

const drawRopePoints = (context, points, color, width) => {
    for (i = 0; i < points.length; i++) {
        let p = points[i];
        const prev = i > 0 ? points[i - 1] : null;
        if(prev) {
            context.beginPath();
            context.moveTo(prev.pos.x, prev.pos.y);
            context.lineTo(p.pos.x, p.pos.y);
            context.lineWidth = width;
            context.strokeStyle = color;
            context.stroke();
        }
    }
};

const draw = (canvas, context, dt) => {
    drawRopePoints(context, points, args.color, args.ropeSize);
};

const app = new App(window, canvas, context, tick, draw, 60);

app.start();

              
            
!
999px

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