Big fps games

When making an Fps game i code things the way i think is right but some times it is not very efficient so i was wondering when you play these big titles such as Call of duty they have a kill streak system and if anyone doesn’t know what that means it basically is how many kills you are on in one life so 5kills in one life if a 5killstreak and when you die it resets to 0 is the most efficient way of doing this by making a variable and on each kill +1 and on death reset to 0 or is there a much easier way that im not thinking off?
Also how can you make your text more lively in the widgets instead of having it static how can i make it jump out at you like this gif? Screen capture - 6a367c8e996ae6b147ef21335a8ca22f - Gyazo how do you make it jump out like this?

regarding the kill streak, the method you mentioned is the only way to do it (barring any ridiculous solution). You just increment a counter and reset it on death.

the only thing happening in that gif is the text gets bigger for a small amount of time whenever it changes