Make a varible for the enemy's health, For the random damage, If you want the damage to change in any way in the future, make 2 varibles, one for min damage and the other for max damage, here is the formula. HP=HP-rnd(MAX-MIN)+MIN
My idea is earth, water and fire. earth beats water beats fire beats earth. Possible sprites: A big drop of water, A ball of fire and a plant for earth. Hope you like!
Okay, first make a @ loop. Then for SPOFS you want to put in somthing like this: SPOFS 1,X,Y . X and Y are the 2 varibles that represent the X,Y Axis. Now to make the sprite move, use IF BUTTON()==[8] THEN {X=X+1}. Reapeat and use 8,4,2,1 in [] for the other directions. In {} use X=X-1,Y=Y+1 and Y=Y-1. Finally put GOTO @LOOP
Same thing happened to me once while playing Smash Bros, It might be the fact that Smash and SB both use lots of data or that theres something with your 3DS XL.