Thanks for the feedback! It's not very clear from the start how the game works. A tutorial section would fix this, thank you for hinting that out! :)
The movement is based on WASD: W and S are used for Acceleration, whilst A and D are used for Steering. In order to move you would need to have either W or S pressed, and use A or D to steer. Pressing A and D would apply only steering. So A or D pressed alone would cause the tank to rotate in a circle.