what are you trying to slow down?
Probably best to set everyone’s speed by a master object that messages all objects.
Reduce the speed in this object would affect all objects its messaging.
Hey, I actually have a good way of doing this!!!
Basically whenever you want to trigger slow motion have each moving object extract their own X and Y volocet and divide by however much slower you want your game to go not perfect but you get the idea.
-Slow motion in my testing game-
http://flowlab.io/game/play/1358250
If you watch Game Maker’s Toolkit, you know that pausing the game multiple times can have a neat effect. Not the same as slow motion, but it can be converted into what you are looking for. Basically, whenever you hit an enemy, pause the game for .2 seconds for some effects.
You can interpret this into ‘pause the game for .1 seconds every .2 seconds’ for slow motion. This will make the game run at 2/3 the speed. The only problem with this solution is you are literally going beyond what the server can handle. For example, imagine if I did that for my Terraria game. 300K blocks with over 10 Million lines of coding stopping and starting every .3 seconds?! You would obliterate flowlab. This is a good solution still, just don’t expect to get away with it if you have some advanced A.I. or an open world game.