Once I speculated about the origins - or the originators - of energy shield in first person shooter games. I came to conclusion - surprise, surprise - that the earliest exponent of the notion, was ‘Quake 2’, with implementation of a device: the power armor or the power shield.
The power shield, was an item - an artifact - which means, it could be turned on or off, as an addon to all other defensive values one would already have. It was using energy cells - the ammo shared with energy-cell based weapons, such as the hyperblaster or the BFG.
The power shield, protected from projectile impact - as far as I remember, it mostly protected only from the frontal impact - but paradoxically, it provided also quite a neat, partial protection against environmental hazards, even the magma! The latter, would not probably stand a test of time, balance-wise speaking - I do not frankly remember the exact clockwork of the power shield, though, therefore, a questionmark.
In the original ‘Quake’, we do have cells and we do have very few weapons, using cells - even though when a weapon already does use the cells, it does so massively. Perhaps - such as with rockets - some alternative way of given ammo utilization, could come in handy?
Should I underscore at this point, that the power shield, is to replace the traditional “colorful” armors.
One could argue, that the power shield equivalent in ‘Quake’, alters the “meatball” style of ‘Quake’ health and damage system. I reply that this only changes the resources in demand, still remaining perfectly within the “meatball” paradigm. The resources in demand, shift from actual medkits, mainly to energy cells. The medkits, are there as before, but to a lesser extent - becoming crucial when the power shield, is down.
Instead of time-based recharging - as it is in some other, non-“meatball” styles - the shield, would require cells to be maintained. Notwithstanding, it is the health factor, that means game over at the state of zero - not the shield.
To spice things up, there could be damage inducing pathways, dealing damage directly unto the health and only partially minding the shield or even despite the shield altogether. Understandably, the latter, should be carefully weighted, otherwise, the gameplay momentum, becomes broken.