.hit
From WikiManual
These give the bots a sense of touch, allowing them to tell when something has hit them or if they have hit something.
A good use of these are with Blind bots to give them some sense of what is going on around them.
hit - Has your bot been hit by another bot?
hitup - hit from the front? hitdn - hit from the back? hitdx - hit on the right? hitsx - hit on the left?