Robo Army is a side-scrolling Beat-'em-up with tons of fun to be had. You are a robot - they are a robot, the dog is a robot, the monkey is a robot - EVERYONE's a robot.
You use the joystick and three buttons... Punch, jump and kick/special. The third button's action is dependent on how many (and what color) power-ups you have collected. There is a bar that shows how many you've collected (and the color) - and you can use the special power as many times as you have little filled globes on that bar. When it runs out, the third button is simply a kick. What happens on the special attack is correlated to how much bar (what color) you have. So, when the bar is full, your attack is the max and when the bar is diminished, the attacks get less and less powerful until it reverts to simply a kick.
So, keep picking up the power-ups to fill this gauge and keep your special attack powerful. There is also another kind of power-up - one that turns you into a vehicle. Then, you use the vehicle to smash into everything else. You don't have to punch or kick when you are in vehicle form, you simply run everything down (kind of like when you are texting and driving in real life).
The graphics are excellent and the sound is definitely a notch above other games of this type and era. Because everything is a robot, you get a lot of metal clanging sounds that really add to the atmosphere.
Other features include the ol' "you can pick anything up and throw it" trick. Also, later stages add some more platform type jumping and climbing.
It mucho-good beat-'em-up fun. The punches land in a satisfying manner and the challenge is good without being ridiculous. Go play it.