diff --git a/demo/client/index.html b/demo/client/index.html
index f304f66f..7b1a37b1 100644
--- a/demo/client/index.html
+++ b/demo/client/index.html
@@ -25,6 +25,7 @@
             }
             #pf-canvas {
                 display: block;
+                touch-action: none;
             }
         </style>
     </head>
diff --git a/demo/client/package.json b/demo/client/package.json
index 2131b2bf..f3ac72b4 100644
--- a/demo/client/package.json
+++ b/demo/client/package.json
@@ -12,6 +12,7 @@
     "@types/node": "^8.0.19",
     "base64-js": "^1.2.1",
     "bootstrap": "^4.0.0-alpha.6",
+    "gl-matrix": "^2.4.0",
     "opentype.js": "^0.7.3",
     "ts-loader": "^2.3.2",
     "typescript": "^2.4.2",
diff --git a/demo/client/src/index.ts b/demo/client/src/index.ts
index 11244894..6e4f7b02 100644
--- a/demo/client/src/index.ts
+++ b/demo/client/src/index.ts
@@ -3,11 +3,14 @@
 // Copyright © 2017 Mozilla Foundation
 
 const base64js = require('base64-js');
+const glmatrix = require('gl-matrix');
 const opentype = require('opentype.js');
 
 const TEXT: string = "O";
 const FONT_SIZE: number = 16.0;
 
+const SCALE_FACTOR: number = 1.0 / 100.0;
+
 const PARTITION_FONT_ENDPOINT_URL: string = "/partition-font";
 
 const COMMON_SHADER_URL: string = '/glsl/gles2/common.inc.glsl';
@@ -26,13 +29,6 @@ const B_QUAD_SIZE: number = 4 * 8;
 const B_QUAD_UPPER_INDICES_OFFSET: number = 0;
 const B_QUAD_LOWER_INDICES_OFFSET: number = 4 * 4;
 
-const IDENTITY: Matrix4D = [
-    1.0, 0.0, 0.0, 0.0,
-    0.0, 1.0, 0.0, 0.0,
-    0.0, 0.0, 1.0, 0.0,
-    0.0, 0.0, 0.0, 1.0,
-];
-
 const SHADER_URLS: ShaderMap<ShaderProgramURLs> = {
     blit: {
         vertex: "/glsl/gles2/blit.vs.glsl",
@@ -73,7 +69,12 @@ interface UnlinkedShaderProgram {
     fragment: WebGLShader;
 }
 
-type Matrix4D = number[];
+type Matrix4D = Float32Array;
+
+interface Point2D {
+    x: number;
+    y: number;
+}
 
 interface Size2D {
     width: number;
@@ -466,7 +467,10 @@ class PathfinderView {
     constructor(canvas: HTMLCanvasElement,
                 commonShaderSource: string,
                 shaderSources: ShaderMap<ShaderProgramSource>) {
+        this.transform = glmatrix.mat4.create();
+
         this.canvas = canvas;
+        this.canvas.addEventListener('wheel', event => this.onWheel(event), false);
 
         this.initContext();
 
@@ -587,6 +591,24 @@ class PathfinderView {
         window.requestAnimationFrame(() => this.redraw());
     }
 
+    onWheel(event: WheelEvent) {
+        if (event.ctrlKey) {
+            // Zoom event: see https://developer.mozilla.org/en-US/docs/Web/Events/wheel
+            const scaleFactor = 1.0 - event.deltaY * window.devicePixelRatio * SCALE_FACTOR;
+            const scaleFactors = new Float32Array([scaleFactor, scaleFactor, 1.0]);
+            glmatrix.mat4.scale(this.transform, this.transform, scaleFactors);
+        } else {
+            const delta = new Float32Array([
+                -event.deltaX * window.devicePixelRatio,
+                event.deltaY * window.devicePixelRatio,
+                0.0
+            ]);
+            glmatrix.mat4.translate(this.transform, this.transform, delta);
+        }
+
+        this.setDirty();
+    }
+
     resizeToFit() {
         const width = window.innerWidth;
         const height = window.scrollY + window.innerHeight -
@@ -628,7 +650,7 @@ class PathfinderView {
     }
 
     setTransformUniform(uniforms: UniformMap) {
-        this.gl.uniformMatrix4fv(uniforms.uTransform, false, IDENTITY);
+        this.gl.uniformMatrix4fv(uniforms.uTransform, false, this.transform);
     }
 
     setFramebufferSizeUniform(uniforms: UniformMap) {
@@ -715,7 +737,6 @@ class PathfinderView {
         this.gl.bindBuffer(this.gl.ELEMENT_ARRAY_BUFFER, this.meshes.coverCurveIndices);
 
         // Draw direct curve parts.
-        this.gl.uniformMatrix4fv(directCurveProgram.uniforms.uTransform, false, IDENTITY);
         this.setTransformUniform(directCurveProgram.uniforms);
         this.setFramebufferSizeUniform(directCurveProgram.uniforms);
         this.pathColorsBufferTexture.bind(this.gl, directCurveProgram.uniforms, 0);
@@ -739,6 +760,9 @@ class PathfinderView {
     quadPositionsBuffer: WebGLBuffer;
     quadTexCoordsBuffer: WebGLBuffer;
     quadElementsBuffer: WebGLBuffer;
+
+    transform: Matrix4D;
+
     dirty: boolean;
 }