Open the game (click here) then select 'Open' when the dialog appears; be sure to do a Save As.. immediately and save it somewhere safe (like your Home directory); otherwise you'll forget later and save it back to the temporary location -- then you'll probably lose it.

This is a simple platform-type game, most of the functionality is achieved with colours:

1. Mario can stand on the black parts.  The soles of his feet are a particular colour and as long as that colour is touching black he doesn't fall.
2. If he touches red he dies.
3. If he touches yellow it changes to the next level.
4. If he touches the coin it disappears.
5. If he touches the Goomba he dies.
6. Use right and left arrow to move Mario
7. Press Space to jump, you can also double-jump by pressing Space twice.
   

The parts to this challenge are (in increasing order of difficulty):

1. Make the second level achievable (ideas: add new blocks, add a ladder, perhaps add some 'fire' to make it harder too).
   
2. Add a new level.
3. Add a score, one point for each coin.
4. Add a new colour that Mario can't walk through and add obstacles to a level using it.
   
5. Add lives, you get three lives at the start and lose a life each time you 'die'.  Dying restarts you back at the start of the level.
6. Make the Goomba move.
7. Add a 'gorilla' who sits at the top and throws bananas down which kill Mario.