I would make them 40x40 at least, as anything below that's a bit tricky to touch, especially if they're moving fast.
You could make the image you use take up the same amount of space as the 32x32 one, but fill the rest of the space with emptiness (so the image looks the same size, but will fit in a 40x40 actor)
Comments
You could make the image you use take up the same amount of space as the 32x32 one, but fill the rest of the space with emptiness (so the image looks the same size, but will fit in a 40x40 actor)
Hope that helps!
QS