…where you are limited to the bottom of the screen, just like in the original Chicken Invaders. Movement can still be done with all current types of control (mouse, keyboard and joystick) but you could only move left and right.
Obviously waves with ommidirection, safe zones in any location but the bottom part of the screen, and to an extent, waves with a zoomed out battlefield would have to be excluded from this gametype.
These missions could be done as one of the daily challenges for us to test it out, then be pushed in the list of missions on planet/star/wormhole in the galaxy.