It seems keys are given away pretty often for this game, and you don't have to play long to understand why.
Let's start with the difficulty options: Hard, Hard, and Hard. There are three buttons, but they do nothing. Oh look, it's an attempt to be clever, or troll the player, or whatever the purpose was. Okay, I get it: No choice, expect rage-quit difficulty.
Except I wouldn't call the game hard. At least the core of it. And I don't normally play these kinds of games. Hell, I beat the first 3 stages just by idling in the same spot on the screen, holding LMB to fire, and occasionally using the special laser attack (RMB), which mows down enemies for a good 5 seconds or so. You can activate a shield with Space, but it doesn't make a difference. If you get hit you lose a life (3 per level) whether you're shielded or not, so I don't see why it was even included. (Maybe another 'hah, we're making this difficult' jab?) Both "abilities" are only usable once per level. They reset when you die.
You're constantly moving forward (WASD adjusts your relative position), shooting stuff that comes flying at you and dodging repetitive obstacles like bugs carrying shields, wrecked bicycle wheels, ground canons, etc. It felt like a cartoony version of those old "fixed shooter" arcade games. Or maybe a weak "runner" game, just in the air and with a couple of weapons at your disposal.
The obstacles are the same in every stage, and in the same locations. Their patterns can be memorized via trial and error. The different swarms of insects are more annoying than difficult. Just stay to the left and keep firing constantly to clear the way, saving your laser attack for the more unpredictable types. The most difficult aspect is probably figuring out the hitbox of each enemy/obstacle/projectile, so you know just how far to nudge to avoid getting hit.
Each level adds a new obstacle/enemy or two, but the overall object is the same: shoot swarms and avoid predictable hazards till you reach the 'end' of a level. It gets boring quickly, because all you're really doing is correcting your errors until the whole level is burned into your brain. It's like the video game equivalent of memorizing a really long and pointless string of numbers. You repeat it over and over and over and over, and eventually you get "good" at it by pure rote. But getting to that point is anything but fun, and there's nothing rewarding about it other than bragging to your friends, who are just gonna roll their eyes at you for attempting it in the first place.
Overall, I'm glad I didn't waste money on this. If you score a free key by all means try it out for yourself (or for the cards), but otherwise there's no point. There are no achievements, the 'plot' and minimal dialogue are hollow and uninteresting, and there's really no incentive to beat the game whatsoever. Save your money.