Source: Dominic Holmes
There is a web page about Rainbow Islands located here:
http://www.cs.uct.ac.za/ stjasink/ri/ http://www.cs.uct.ac.za/~stjasink/ri/
The pages are by Stephen Tjasink and contain a lot of information about the game.
Source: ?????
Make sure the second to last 2 digits of your score are the same when you reach 'goal in', this will make the chest contain a better bonus item.eg. reach goal in with a score of xxxx11x to get a chest full of ?????.