Straight lines

[smoque]

first, I love this app
second, I don't know if it's a glitch or not, but using two fingers, I use both index fingers, and alternately tapping, with experimentation you'll find you can do straight lines.
I find it works best to lay the fingers on the a and b points, then lifting first on point a, then b

[monsterblues]

Great tip! I'm sure its just a happy accident though.