diff --git a/src/gravity-points/app.js b/src/gravity-points/app.js
new file mode 100644
index 0000000..8673ec2
--- /dev/null
+++ b/src/gravity-points/app.js
@@ -0,0 +1,532 @@
+/**
+ * requestAnimationFrame
+ */
+window.requestAnimationFrame = (function(){
+    return  window.requestAnimationFrame       ||
+            window.webkitRequestAnimationFrame ||
+            window.mozRequestAnimationFrame    ||
+            window.oRequestAnimationFrame      ||
+            window.msRequestAnimationFrame     ||
+            function (callback) {
+                window.setTimeout(callback, 1000 / 60);
+            };
+})();
+
+
+/**
+ * Vector
+ */
+function Vector(x, y) {
+    this.x = x || 0;
+    this.y = y || 0;
+}
+
+Vector.add = function(a, b) {
+    return new Vector(a.x + b.x, a.y + b.y);
+};
+
+Vector.sub = function(a, b) {
+    return new Vector(a.x - b.x, a.y - b.y);
+};
+
+Vector.scale = function(v, s) {
+    return v.clone().scale(s);
+};
+
+Vector.random = function() {
+    return new Vector(
+        Math.random() * 2 - 1,
+        Math.random() * 2 - 1
+    );
+};
+
+Vector.prototype = {
+    set: function(x, y) {
+        if (typeof x === 'object') {
+            y = x.y;
+            x = x.x;
+        }
+        this.x = x || 0;
+        this.y = y || 0;
+        return this;
+    },
+
+    add: function(v) {
+        this.x += v.x;
+        this.y += v.y;
+        return this;
+    },
+
+    sub: function(v) {
+        this.x -= v.x;
+        this.y -= v.y;
+        return this;
+    },
+
+    scale: function(s) {
+        this.x *= s;
+        this.y *= s;
+        return this;
+    },
+
+    length: function() {
+        return Math.sqrt(this.x * this.x + this.y * this.y);
+    },
+
+    lengthSq: function() {
+        return this.x * this.x + this.y * this.y;
+    },
+
+    normalize: function() {
+        var m = Math.sqrt(this.x * this.x + this.y * this.y);
+        if (m) {
+            this.x /= m;
+            this.y /= m;
+        }
+        return this;
+    },
+
+    angle: function() {
+        return Math.atan2(this.y, this.x);
+    },
+
+    angleTo: function(v) {
+        var dx = v.x - this.x,
+            dy = v.y - this.y;
+        return Math.atan2(dy, dx);
+    },
+
+    distanceTo: function(v) {
+        var dx = v.x - this.x,
+            dy = v.y - this.y;
+        return Math.sqrt(dx * dx + dy * dy);
+    },
+
+    distanceToSq: function(v) {
+        var dx = v.x - this.x,
+            dy = v.y - this.y;
+        return dx * dx + dy * dy;
+    },
+
+    lerp: function(v, t) {
+        this.x += (v.x - this.x) * t;
+        this.y += (v.y - this.y) * t;
+        return this;
+    },
+
+    clone: function() {
+        return new Vector(this.x, this.y);
+    },
+
+    toString: function() {
+        return '(x:' + this.x + ', y:' + this.y + ')';
+    }
+};
+
+
+/**
+ * GravityPoint
+ */
+function GravityPoint(x, y, radius, targets) {
+    Vector.call(this, x, y);
+    this.radius = radius;
+    this.currentRadius = radius * 0.5;
+
+    this._targets = {
+        particles: targets.particles || [],
+        gravities: targets.gravities || []
+    };
+    this._speed = new Vector();
+}
+
+GravityPoint.RADIUS_LIMIT = 65;
+GravityPoint.interferenceToPoint = true;
+
+GravityPoint.prototype = (function(o) {
+    var s = new Vector(0, 0), p;
+    for (p in o) s[p] = o[p];
+    return s;
+})({
+    gravity:       0.05,
+    isMouseOver:   false,
+    dragging:      false,
+    destroyed:     false,
+    _easeRadius:   0,
+    _dragDistance: null,
+    _collapsing:   false,
+
+    hitTest: function(p) {
+        return this.distanceTo(p) < this.radius;
+    },
+
+    startDrag: function(dragStartPoint) {
+        this._dragDistance = Vector.sub(dragStartPoint, this);
+        this.dragging = true;
+    },
+
+    drag: function(dragToPoint) {
+        this.x = dragToPoint.x - this._dragDistance.x;
+        this.y = dragToPoint.y - this._dragDistance.y;
+    },
+
+    endDrag: function() {
+        this._dragDistance = null;
+        this.dragging = false;
+    },
+
+    addSpeed: function(d) {
+        this._speed = this._speed.add(d);
+    },
+
+    collapse: function(e) {
+        this.currentRadius *= 1.75;
+        this._collapsing = true;
+    },
+
+    render: function(ctx) {
+        if (this.destroyed) return;
+
+        var particles = this._targets.particles,
+            i, len;
+
+        for (i = 0, len = particles.length; i < len; i++) {
+            particles[i].addSpeed(Vector.sub(this, particles[i]).normalize().scale(this.gravity));
+        }
+
+        this._easeRadius = (this._easeRadius + (this.radius - this.currentRadius) * 0.07) * 0.95;
+        this.currentRadius += this._easeRadius;
+        if (this.currentRadius < 0) this.currentRadius = 0;
+
+        if (this._collapsing) {
+            this.radius *= 0.75;
+            if (this.currentRadius < 1) this.destroyed = true;
+            this._draw(ctx);
+            return;
+        }
+
+        var gravities = this._targets.gravities,
+            g, absorp,
+            area = this.radius * this.radius * Math.PI, garea;
+
+        for (i = 0, len = gravities.length; i < len; i++) {
+            g = gravities[i];
+
+            if (g === this || g.destroyed) continue;
+
+            if (
+                (this.currentRadius >= g.radius || this.dragging) &&
+                this.distanceTo(g) < (this.currentRadius + g.radius) * 0.85
+            ) {
+                g.destroyed = true;
+                this.gravity += g.gravity;
+
+                absorp = Vector.sub(g, this).scale(g.radius / this.radius * 0.5);
+                this.addSpeed(absorp);
+
+                garea = g.radius * g.radius * Math.PI;
+                this.currentRadius = Math.sqrt((area + garea * 3) / Math.PI);
+                this.radius = Math.sqrt((area + garea) / Math.PI);
+            }
+
+            g.addSpeed(Vector.sub(this, g).normalize().scale(this.gravity));
+        }
+
+        if (GravityPoint.interferenceToPoint && !this.dragging)
+            this.add(this._speed);
+
+        this._speed = new Vector();
+
+        if (this.currentRadius > GravityPoint.RADIUS_LIMIT) this.collapse();
+
+        this._draw(ctx);
+    },
+
+    _draw: function(ctx) {
+        var grd, r;
+
+        ctx.save();
+
+        grd = ctx.createRadialGradient(this.x, this.y, this.radius, this.x, this.y, this.radius * 5);
+        grd.addColorStop(0, 'rgba(0, 0, 0, 0.1)');
+        grd.addColorStop(1, 'rgba(0, 0, 0, 0)');
+        ctx.beginPath();
+        ctx.arc(this.x, this.y, this.radius * 5, 0, Math.PI * 2, false);
+        ctx.fillStyle = grd;
+        ctx.fill();
+
+        r = Math.random() * this.currentRadius * 0.7 + this.currentRadius * 0.3;
+        grd = ctx.createRadialGradient(this.x, this.y, r, this.x, this.y, this.currentRadius);
+        grd.addColorStop(0, 'rgba(0, 0, 0, 1)');
+        grd.addColorStop(1, Math.random() < 0.2 ? 'rgba(255, 196, 0, 0.15)' : 'rgba(103, 181, 191, 0.75)');
+        ctx.beginPath();
+        ctx.arc(this.x, this.y, this.currentRadius, 0, Math.PI * 2, false);
+        ctx.fillStyle = grd;
+        ctx.fill();
+        ctx.restore();
+    }
+});
+
+
+/**
+ * Particle
+ */
+function Particle(x, y, radius) {
+    Vector.call(this, x, y);
+    this.radius = radius;
+
+    this._latest = new Vector();
+    this._speed  = new Vector();
+}
+
+Particle.prototype = (function(o) {
+    var s = new Vector(0, 0), p;
+    for (p in o) s[p] = o[p];
+    return s;
+})({
+    addSpeed: function(d) {
+        this._speed.add(d);
+    },
+
+    update: function() {
+        if (this._speed.length() > 12) this._speed.normalize().scale(12);
+
+        this._latest.set(this);
+        this.add(this._speed);
+    }
+
+    // render: function(ctx) {
+    //     if (this._speed.length() > 12) this._speed.normalize().scale(12);
+
+    //     this._latest.set(this);
+    //     this.add(this._speed);
+
+    //     ctx.save();
+    //     ctx.fillStyle = ctx.strokeStyle = '#fff';
+    //     ctx.lineCap = ctx.lineJoin = 'round';
+    //     ctx.lineWidth = this.radius * 2;
+    //     ctx.beginPath();
+    //     ctx.moveTo(this.x, this.y);
+    //     ctx.lineTo(this._latest.x, this._latest.y);
+    //     ctx.stroke();
+    //     ctx.beginPath();
+    //     ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false);
+    //     ctx.fill();
+    //     ctx.restore();
+    // }
+});
+
+
+
+// Initialize
+
+(function() {
+
+    // Configs
+
+    var BACKGROUND_COLOR      = 'rgba(11, 51, 56, 1)',
+        PARTICLE_RADIUS       = 1,
+        G_POINT_RADIUS        = 10,
+        G_POINT_RADIUS_LIMITS = 65;
+
+
+    // Vars
+
+    var canvas, context,
+        bufferCvs, bufferCtx,
+        screenWidth, screenHeight,
+        mouse = new Vector(),
+        gravities = [],
+        particles = [],
+        grad,
+        gui, control;
+
+
+    // Event Listeners
+
+    function resize(e) {
+        screenWidth  = canvas.width  = window.innerWidth;
+        screenHeight = canvas.height = window.innerHeight;
+        bufferCvs.width  = screenWidth;
+        bufferCvs.height = screenHeight;
+        context   = canvas.getContext('2d');
+        bufferCtx = bufferCvs.getContext('2d');
+
+        var cx = canvas.width * 0.5,
+            cy = canvas.height * 0.5;
+
+        grad = context.createRadialGradient(cx, cy, 0, cx, cy, Math.sqrt(cx * cx + cy * cy));
+        grad.addColorStop(0, 'rgba(0, 0, 0, 0)');
+        grad.addColorStop(1, 'rgba(0, 0, 0, 0.35)');
+    }
+
+    function mouseMove(e) {
+        mouse.set(e.clientX, e.clientY);
+
+        var i, g, hit = false;
+        for (i = gravities.length - 1; i >= 0; i--) {
+            g = gravities[i];
+            if ((!hit && g.hitTest(mouse)) || g.dragging)
+                g.isMouseOver = hit = true;
+            else
+                g.isMouseOver = false;
+        }
+
+        canvas.style.cursor = hit ? 'pointer' : 'default';
+    }
+
+    function mouseDown(e) {
+        for (var i = gravities.length - 1; i >= 0; i--) {
+            if (gravities[i].isMouseOver) {
+                gravities[i].startDrag(mouse);
+                return;
+            }
+        }
+        gravities.push(new GravityPoint(e.clientX, e.clientY, G_POINT_RADIUS, {
+            particles: particles,
+            gravities: gravities
+        }));
+    }
+
+    function mouseUp(e) {
+        for (var i = 0, len = gravities.length; i < len; i++) {
+            if (gravities[i].dragging) {
+                gravities[i].endDrag();
+                break;
+            }
+        }
+    }
+
+    function doubleClick(e) {
+        for (var i = gravities.length - 1; i >= 0; i--) {
+            if (gravities[i].isMouseOver) {
+                gravities[i].collapse();
+                break;
+            }
+        }
+    }
+
+
+    // Functions
+
+    function addParticle(num) {
+        var i, p;
+        for (i = 0; i < num; i++) {
+            p = new Particle(
+                Math.floor(Math.random() * screenWidth - PARTICLE_RADIUS * 2) + 1 + PARTICLE_RADIUS,
+                Math.floor(Math.random() * screenHeight - PARTICLE_RADIUS * 2) + 1 + PARTICLE_RADIUS,
+                PARTICLE_RADIUS
+            );
+            p.addSpeed(Vector.random());
+            particles.push(p);
+        }
+    }
+
+    function removeParticle(num) {
+        if (particles.length < num) num = particles.length;
+        for (var i = 0; i < num; i++) {
+            particles.pop();
+        }
+    }
+
+
+    // GUI Control
+
+    control = {
+        particleNum: 100
+    };
+
+
+    // Init
+
+    canvas  = document.getElementById('c');
+    bufferCvs = document.createElement('canvas');
+
+    window.addEventListener('resize', resize, false);
+    resize(null);
+
+    addParticle(control.particleNum);
+
+    canvas.addEventListener('mousemove', mouseMove, false);
+    canvas.addEventListener('mousedown', mouseDown, false);
+    canvas.addEventListener('mouseup', mouseUp, false);
+    canvas.addEventListener('dblclick', doubleClick, false);
+
+
+    // GUI
+
+    gui = new dat.GUI();
+    gui.add(control, 'particleNum', 0, 500).step(1).name('Particle Num').onChange(function() {
+        var n = (control.particleNum | 0) - particles.length;
+        if (n > 0)
+            addParticle(n);
+        else if (n < 0)
+            removeParticle(-n);
+    });
+    gui.add(GravityPoint, 'interferenceToPoint').name('Interference Between Point');
+    gui.close();
+
+
+    // Start Update
+
+    var loop = function() {
+        var i, len, g, p;
+
+        context.save();
+        context.fillStyle = BACKGROUND_COLOR;
+        context.fillRect(0, 0, screenWidth, screenHeight);
+        context.fillStyle = grad;
+        context.fillRect(0, 0, screenWidth, screenHeight);
+        context.restore();
+
+        for (i = 0, len = gravities.length; i < len; i++) {
+            g = gravities[i];
+            if (g.dragging) g.drag(mouse);
+            g.render(context);
+            if (g.destroyed) {
+                gravities.splice(i, 1);
+                len--;
+                i--;
+            }
+        }
+      
+        bufferCtx.save();
+        bufferCtx.globalCompositeOperation = 'destination-out';
+        bufferCtx.globalAlpha = 0.35;
+        bufferCtx.fillRect(0, 0, screenWidth, screenHeight);
+        bufferCtx.restore();
+
+        // パーティクルをバッファに描画
+        // for (i = 0, len = particles.length; i < len; i++) {
+        //     particles[i].render(bufferCtx);
+        // }
+        len = particles.length;
+        bufferCtx.save();
+        bufferCtx.fillStyle = bufferCtx.strokeStyle = '#fff';
+        bufferCtx.lineCap = bufferCtx.lineJoin = 'round';
+        bufferCtx.lineWidth = PARTICLE_RADIUS * 2;
+        bufferCtx.beginPath();
+        for (i = 0; i < len; i++) {
+            p = particles[i];
+            p.update();
+            bufferCtx.moveTo(p.x, p.y);
+            bufferCtx.lineTo(p._latest.x, p._latest.y);
+        }
+        bufferCtx.stroke();
+        bufferCtx.beginPath();
+        for (i = 0; i < len; i++) {
+            p = particles[i];
+            bufferCtx.moveTo(p.x, p.y);
+            bufferCtx.arc(p.x, p.y, p.radius, 0, Math.PI * 2, false);
+        }
+        bufferCtx.fill();
+        bufferCtx.restore();
+
+        // バッファをキャンバスに描画
+        context.drawImage(bufferCvs, 0, 0);
+
+        requestAnimationFrame(loop);
+    };
+    loop();
+
+})();
+
diff --git a/src/gravity-points/index.html b/src/gravity-points/index.html
new file mode 100644
index 0000000..28147b8
--- /dev/null
+++ b/src/gravity-points/index.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="utf-8"/>
+        <title>Fizzy Sparks</title>
+        <link href="style.css" rel="stylesheet" />
+        <script src="https://cdnjs.cloudflare.com/ajax/libs/dat-gui/0.5/dat.gui.min.js"></script>
+        <script type="module" src="app.js"></script>
+    </head>
+    <body>
+        <canvas id="c"></canvas>
+        <div class="info">Click to add gravity point.</div>
+    </body>
+</html>
+
diff --git a/src/gravity-points/style.css b/src/gravity-points/style.css
new file mode 100644
index 0000000..4183c94
--- /dev/null
+++ b/src/gravity-points/style.css
@@ -0,0 +1,28 @@
+body {
+    font-family: Helvetica sans-serif;
+    padding: 0;
+    margin: 0;
+    background-color: #222;
+    overflow: hidden;
+    -webkit-user-select: none;
+       -moz-user-select: none;
+         -o-user-select: none;
+        -ms-user-select: none;
+            user-select: none;
+}
+
+canvas {
+    position: absolute;
+    top: 0;
+    left: 0;
+}
+
+.info {
+    position: absolute;
+    top: 0;
+    left: 0;
+    padding: 5px 15px;
+    color: #eee;
+    font-size: 13px;
+    background-color: rgba(0, 0, 0, .5);
+}
diff --git a/src/index.html b/src/index.html
index 5abfa67..9b77fc7 100644
--- a/src/index.html
+++ b/src/index.html
@@ -15,6 +15,7 @@
             <li> <a href="./orbital-trails/index.html">Orbital Trails (mine)</a>
             <li> <a href="./bokeh/index.html">Bokeh effect (their)</a>
             <li> <a href="./sparks/index.html">Sparks (theirs)</a>
+            <li> <a href="./gravity-points/index.html">Gravity Points (theirs)</a>
         </ul>
     </body>
 </html>