I'm absolutely loving the program, here's my first(/a test) doodle in it when I was messing around.
However, I want to address some issues I had with it...
Can you make an option removing the cursor details..? I do like the colorful cursor and, the spinning parts it has I do but, after a while, it gets really hard for me to focus on the cursor itself and, the colorful nature of it makes it hard to see... I don't care if the cursor is black or, grey, I just can't see it personally and, in general it really hurts my eyes now, I'm aware this is a bit of a nit pick but, I just had to bring it up.
Also, do you think you'll add a fill tool? I'm aware of the undo(/redo) button is a feature people want as well but, I'm personally curious of a fill tool( now to be honest I'm not sure if Flipnote even had a fill tool in the first place so, this also might be a nit pick).