Add holes.  They are black.

They're really black, so you mostly can't see them, except where they block the stars... and of course, by their effect on objects around them.  They impose their own gravity on falling objects nearby.  Objects that get too close, and are destructible (currently just blocks), will take heavy damage if they get close enough to touch.

Bit more math applied to pellets.  Under normal gravity conditions, the pellet will be fired in an arc to pass through the point that was clicked.  When firing upward, the peak of the curve touches the mouse position.  When firing downward, it is actually fired left or right -- gravity is allowed to add the downward motion.  All bets are off when a black hole is around.  Since pellets are indestructible except when they hit something, and they don't hit black holes, they are capable of orbiting a hundred times or more... if fired in just the right trajectory.

It's now possible to delete objects by pointing at them and hitting Delete.  When deleting a teleporter or its destination, both objects will go away.