Please have a look at https://www.greenfoot.org/topics/64967/0 There is a menu to choose which ship the hero is flying. You can reuse it for your idea, especially adding buttons for each position to the chooser-menu. At the button action, you can also add a check whether the hero has enough coins and the reduction of coins when the number of coins is sufficient. You can also add booleans to the hero class to indicate whether the effects are already bought. Please let me know whether this helps, otherwise just add additional questions as response here to resolve any remaining problems.