Press t with the mouse-pointer on an object to delete it, press c with the mouse-pointer on a coloured object to change its colour, & click the copy-paste button to, well, you know.
Robtop, for making GD. V1.0 done before shared. UPDATES 1.3, it's out at long last! New things: Coloured objects, another song. Minor update: 1.3.1! You can now toggle between backgrounds! Minor update: 1.3.2! New black background! Minor update: 1.3.3! You can now toggle between background colours!
