It's literally Earthsiege, though that much is apparent from the name.
Not much to comment about regarding the gameplay at this time. Fire doesn't work (if X was meant to fire) and presently the mech doesn't respect the height of the terrain they're on. Art looks spot on - but I'm not sure how much of it is just directly taken from Earthsiege itself.
One hell of a nostalgia wave from me watching the mech hanger light up again after all this time. Will you have the flying mech in the game?