Alright, I just set the needed events up and tested it, it works, so here's what you have to do:
View attachment 1981 View attachment 1982
You create a new common event, [first pic] and in it you create a conditional branch wherein you state that if the script shown in the pic is triggered (here's the code for you to copy: Input.keyTriggered("C") ) a screen flash will occur. The common event must be set to parallel (marked in yellow) and must be triggered by a switch (marked in red). From there on out, you just create an event on your map [second pic] (starting map would be convenient, whatever suits you, as the switch stays on), which's trigger is set to parallel (marked in yellow) and let the event set the switch for the common event to ON. That should set you up ready to go ^^ As I said, I tested it, and now whenever you press the C button the game flashes. I think, that's what you wanted, right? I hope that helped you :)