Ammo Counters.

For as long as there have been video  games, there have been ammo counters. They are entirely unglamorous readouts  of how many bullets you've got left. For decades they have occupied a portion  of almost every single shooter's UI.

They're so standard, so perfunctory,  so boring as to be nearly invisible. But some are more interesting than others, and over the years the predominant  way of displaying ammo has changed.

They needn't be boring, they can be quite in your  face - and sometimes, you don't need one at all.

Let's start in 1975, 3 years  before Space Invaders. Taito and Midway released an arcade game called Gun Fight.

It was based on an old electromechanical game  from SEGA, transposing its analogue Western action to the digital realm. It might be the first  ever video game to feature an ammo counter.

It's 1v1 combat. Two cowboys, 6  bullets and a duel to the death. The ammo counter is at the bottom  of the screen. A pictographic representation of each player's  bullets - up to 6 icons across.

There's destructible cover in the form of cacti, and a moving stagecoach in later levels. You  move, you shoot, and hopefully don't die.

What I like about Gun Fight is that your ammo  actually matters - with only 6 rounds and no reloads, if one player is empty they  can't win - they can only force a draw.

At a glance, the players can tell that one of them is vulnerable - and the other has  a finite number of chances to win.

It's this sort of tension that underpins  the whole rationale behind having limited ammunition. And yet - most modern games  don't do it nearly as well as Gun Fight.

Now, most shooters of this era didn't  count your shots - Space Invaders, Asteroids etc. gave you unlimited ammunition.

But in the cases where you  do have a finite supply, a pictographic representation seems to  be the most popular method of display.