You can comment out the prepare method (label it as the level one map) and remove the call to that method in the constructor; then, construct you second world and save the world to get the code for that level. Do the same with the second level to start a third, and so on. When all levels are complete, you will need to use a series of 'if-else's depending on the value of the field holding the current level number (or a 'switch' block). Thus, putting all the level maps in the 'prepare' method. Are you using a gridded world (world with a cell size of greater than one)? If so, check out my MapWorld SuperClass scenario.