If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Wreck all the cars on the track as fast as possible. Move your crane with the arrow keys up/down and swing it with arrow keys left/right. Watch the shadow to see what lane your crane is in
Wreck all the cars on the track with your crane demolisher. Move your crane with the arrow keys. You can swing your demolisher with the arrow keys left and right. Watch the shadow of the demolisher to see what lane it is in.