- .up accelerates the robot forward in its eye direction. It uses memory location 1 of the bot to store how much it accelerates in that direction.
10 1 store
This puts 10 on the stack. Than it puts 1 on the stack. Than it stores 10 in memory location 1 of the bot (.up) and removes 1 and 10 from the stack. The 10 in memory location 1 of the bot accelerates it +10 forward in its eye direction if it has not reached the maximum acceleration in that direction.
A robot with this gene would constantly accelerate forward in its eye direction at a rate of 10 per turn. That is to say that his velocity in that direction would increase by a value of 10. If it should rotate then the direction in which the acceleration takes place would also change.
Movement values get cut above 1000 and below -1000, then added up to a single vector including tie and other propulsion vectors, then the vector gets cut to a length of 40 as maximum aceleration.
More details at Movement.