Threejs extrude geometry

gistfile1.js

 //use Extrude Geometry to give it depth, and add it to the scene.                     
       var geometry = new THREE.ExtrudeGeometry( cube,
       {
            bevelEnabled: false, bevelSegments: 0, steps:20, amount: 80
       });                                                 

     //we're using a dark gray flat material
     cubeMesh = new THREE.Mesh( geometry, new THREE.MeshLambertMaterial( {
          color: 0x333333,
          shading: THREE.FlatShading                   
     }));