When thinking about what a mech is we had 2 starting conditions:
- It should be perceived as a vehicle. We are a mech shooter, not a reskin of a usual human shooter.
- It should stay casual. No burden of knowledge on mech construction, and no unnecessary penalties.
Vehicle feeling: apart from art components (movement animations) and dynamics balance (feeling of weight, speed), this is also a gameplay mechanics requirement. What usually separates vehicles from living combatants? Our answer is 'being modular'. If the game is not hard-boiled MilSim, human characters are "whole". Our mechs are made of 4 parts - torso, chassis and 2 shoulders. This has some implications for gameplay mechanics and building principles.
No burden of knowledge: Typically different modules have different purposes. Providing mobility, offence, storing fuel/ammo, etc. They should have something to be meaningful. But at the same time, our mechs are vastly different in shapes and geometry. We wanted to have meaning to mech modules but avoid forcing players to learn the composition of each possible mech detail and its purpose. Like in tank games players memorize where are fuel tanks in each tank.
No penalties: Another typical part of vehicle shooters is penalties. Destroyed wheels limit mobility, and damaged weapons limit offence. But the vehicle stays functional even with some structural damage. This creates this feeling of modularity and being a vehicle, not a human. But we wanted to avoid that as well. There's no need to slow gameplay down or force players to play a half-functioning entity.
So together this was quite a conundrum: we wanted to have modularity, but avoid all typical implications and effects that modules bring to the game. Our solution to that was the HP system:
Mech is made of 4 modules, and each module has its own HP. To kill a mech you need to destroy any one of the modules, doesn't matter which particular. Before damaging modules player needs to get through the energy shield protecting the mech.
In my opinion, that's a pretty good solution. It fulfils all the conditions above while also creating some interesting dynamics.
1) This mechanic allows having more weapon dichotomies. In addition to typical burst/sustained, direct/indirect there's also spread/precision. There can be weapons that deal high DPS but distribute it over the whole mech with spread. Or there can be low-ish DPS weapons, but their precision allows the player to focus a module and keep high lethality. So there are weapons good for softening target in general and weapons better for finishing an enemy off.
2) This HP system separates good players from great. By utilizing all mobility options and map elements better players can distribute incoming damage over the mech increasing lifetime.
So overall this system gives us all - creates a mech feeling in gameplay mechanics, provides more design space for content and rewards players for skill. Nifty I'd say.