A little late, but for those of you still checking things out:
Q - "super shot" for your team. Much more damage for 15 seconds
W - spawn a super mini-mech
E - Shield for you main mech
R - Repair a portion of your health (red bar)
T - select a new skill
A (lightning bolt skill) - Super skill that...??? :)
Red Bar - main mech health
Blue Bar - Allied Base health
Earn new skills after destroying 5, 15, 30, and 65 opposing units.