A very quick tutorial to make an armor that covers your health the same way grand theft auto does it. You might be continuing from my last tutorial. And maybe you still have the .capx. If not I'll link this one when I'm done. Weather you continue from this .capx or from the .capx from my last tutorial, make sure along with the health Global variable you have an armor global variable. And you pretty much want to clone everything from health and make it armor (except for maxhealth unless you want to have your max armor controlled my leveling.) Add a text for armor next to your health, and a pick up for armor.
Now to make the armor work until it runs out, every time you would take damage you would have a sub event checking if the armor is above 0, if it is - the armor takes the damage, and another sub event if the armor is equal to or below 0 - the health takes the damage. Another clean little touch to add to it is to make it so when armor is 0 or less, it sets the text invisible, and if its above 0 it sets the text visible. I typically make my armor max out at 100 permanently so i would add an event that if your armor is over 100, it would set back to 100. And make it so if you already have 100 armor you cant pick up the armor.