I would run a parallel process that constantly updates a bunch of variables that keeps track of the player's X and Y, and the X or Y of the things that shoot at you. This is the easy part though.
The more complicated part would be getting the projectiles to spawn correctly and detect when they hit the player (Event Touch is quite unreliable when it comes to triggering on moving targets). Unless you're using a script, your events will have extremely long conditional checks which in turn might add lag.
Maybe someone else has an easier to way make it, but to me it seems like it'll be a fairly large challenge to tackle.
