Drag the points around and "oooooh" :P I allowed for a 0.1 second delay between renderings so that it gives time for the computer to process mouse drags.
Well, looks like I found another ye-olde Scratch project I've been waiting to share for the past, uh, 5 months. xD I guess I quit working on this after my rusty geometry skills couldn't get the maths right. Since then I've improved a lot. Oh, and I have some special blocks inside for you to use! :D