Bad Caterpillar (Steam key/Region free).

http://store.steampowered.com/app/447950/
Partake in a 2D retro action the likes of which hasn’t been seen since the collapse of the arcades decades ago. Experience intense non-stop action as you fight off space insect hordes, collect weapons and power-ups, and battle for high score bragging rights against the entire world. And you know, save mankind from extinction at the hands of caterpillars, scorpions, spiders, and a slew of other ill-tempered giant killer insects.