This is really cool :D I see you have started to work on adding elements.
Take a look at one of @boxmein's projects: http://boxmein.net/tpt/tptkeys/ you can bookmark it if you want to use it in the future. It has (I think) all TPT keyboard shortcuts that might help you.
Also some things that I've noticed:
There is a spot at the bottom where you can't draw on.
Sometimes when you hold click and move your mouse over that spot where you can't draw on and release your finger (AKA stop drawing) and move your mouse upwards to the spot where you can draw on, the brush won't stop drawing even though you aren't holding click (I hope that didn't confuse you, I'm bad at describing :P).
you can make your brush size really really huge and when you move half of the brush to a side, the other half of the brush will appear in the other side.
Please keep up the good work :D
I got it. (I think I'm worse :P)
The spot at the bottom is outside TPT box (which means you shouldn't draw there). Currently nothing is drawn at the bottom yet. However when I move my mouse at the bottom, onmousemove() was not triggered. I can not understand why. Perhaps this is the problem. If mousemove() is not triggered I can not detect mouse up events, so my script will think you're still holding your mouse. Also you're not supposed to move your mouse outside the box since I can not detect mouseup and mousedown outside it.
Half brush will appear in the other side. I've detected the problem but I haven't fixed it yet.
I'm afraid I'll just begin the work and not keep it up because there's only one week left, winter holidays are quite short :) but you can help me as well.
Sorry man :( I'm not good at js.
I don't get it. What is your browser version? Did the brush size become a float number?
I said this is just a concept which isn't supposed to work nicely; I'm talking about an idea which needs a lot of coding.
May I do that after I add at least 2 elements.
wow im amazed +1 if i could :D