The game doesn't tell you but you can use the left right and down keys too. Try to squat and kick the ground to flip the computer lol. Such a strange game.
Twenty-four Karats of Fury
Dude! You just completed the Twenty-four Karats of Fury achievement in Mechanical Commando and won the Twenty-four Karats of Fury badge and 60 points!
found a bug in which after the train explodes, on the last fire, if you jump and it hits you, you'll get pushed forward. You hold forward this entire time and u'll fall through the ground and die..
 "Battalion Commander"){kind=icon}
 "Wrestle Jump"){kind=icon}
 "Mechanical Commando"){kind=icon}
 "Meat Boy"){kind=icon}
 "intrusion"){kind=icon}
 "Dog Eat Dog"){kind=icon}
 "Bubble Tanks 2"){kind=icon}
 "Rapid Reaction Master"){kind=icon}