I am playing BattelTech since I was in 8th grade or so. It was the second "big" game I got into after Warhammer Fantasy Battles 4e. Meanwhile the rules changed a couple times (though not drastically), FASA does not have the license anymore (now with Catalyst Game Labs), but we still play it, mostly with the newest rules.

It is a quite detailed game played on a hex grid. You have movement points, moving one hex costs one (except wooded, level change, than it is more expensive), turning one hex side costs a point, etc.

Ranged combat means choosing your weapons, which have different ranges, always given in three range bands, shooting a enemies farther away means negative modifiers. Your own and the enemies movement give negative modifiers, terrain gives negative modifiers. You need to reach or exceed your target value on 2d6, target values of 12+ cannot be hit. Energy weapons are fed by the reactor, and can shoot unlimited, projectile and missile weapons have limited ammo which you need to keep track of.

Once hit, you roll 2d6 to determine which part of the enemy 'Mech you hit (arms, legs, left/right/center torso, head). Then you do damage to that zone. Each zone has hit points, once these are depleted, damage goes to the internal structure of the 'Mech. With each hit on internal structure you have a chance of inflicting critical hits, damaging weapons, arm actuators, the reactor, etc. Or ammo. Hitting ammo is not good…

So each 'Mech has an armour diagram, torsi have an additional rear armour diagram; an internal structure diagram; a detailed list of where which component of the 'Mech has been installed; weapon info; movement info. So for one model on the board you have one A4 sheet.

Close combat works basically the same as shooting, you need to be in an adjacent hex field, then can kick, punch, ram opponents. Once hit, you also randomly roll where you hit. The main difference is, kicks can only hit enemy legs, punches can anything but the legs.

Everything creates heat: the movement type you choose, the weapons you fire, etc. Each 'Mech has a certain amount of heat sinks, which can negate the built up heat. You can overheat your 'Mech, but you start to accumulate negative modifers; you get negative modifiers to hit, you get slower, you ammo might explode, at certain intervals are safety measures that auto-shutdown you machine if you do not manage to intervene in time. If, during following turns, you create less heat than you can dissipate, you can reduce your excess heat again, and the negative effects of overheating cease to apply.

A detailed game which gets very time consuming quickly, the more 'Mechs you add, but a style of game I like.

And then you can add infantry, tanks, helicopters, aero support…