Collision Sprite Masks in version 99.72

Hey folks,

I feel a little silly about this one.

I can't seem to figure out how to draw custom sprite collision masks in the newest unstable version of Construct. I click on the collision mask button and the red box appears but i don't know how to edit it.

Help?

Construct initially copies the sprite image to the collision mask. Once in collision mask editing mode just draw like you normally would, this does not affect your original image.

Oh. I must be confused because all of the sprites i'm working with are white.

Thanks for the tip.

there's a button next to the collision mask button (I think) that turns the background dark