Well, after quite some time in front of my computer I finally came to a playable demo where you can drive your tank through a 9-color landscape and fire you bullets as much as you want . Actually I used an indexed-colormap in gimp to convert a baked colormap in order to fit the color-constraint.
1-Left 3-right 8-forward 9-backward 0-fire
You can start the game from the website with java-webstart. Follow this link:
You will need java to start the game. (Just try what happens if you press the button! If it does not work, plz tell me your configuration…)