UFO99 is an interesting game, you play as a UFO that is trying to kill all these bizarre block creatures and to be honest, it's not that bad. Gameplay wise, the controls are very simple. You just need to move around with the left thumb virtual joystick and activate the electric shield with your other thumb.
All while trying to dodge the alien creatures that shoot at you and use their extended appendages to kill you, while you try and pick up the bombs, and hammers to kill them, and collect the gas tanks to extend your time. Honestly once you learn the timing on when to use your electric shield, and realise that the shield also gives you a burst of speed, you can manage to get to the boss encounters pretty easily.
The game also has a nearby internet multiplayer mode as well as many different avatars for you to use, though majority of them not only cost gold to purchase, but also IRL currency as well. There are ads, though I don't find them too annoying, and any single purchase will remove the ads from your game. Visually the game is bright, and colourful. With a very crisp and clear pixel art aesthetic.
This game is super cute and I love the visuals of it. Overall I'd say that UFO99 is a super cute casual game that isn't that hard once you know how to use the shield to your advantage. There is a fair amount of in game purchases in the game, and if you want to use a specific cute avatar for your UFO, you will need to pay for it, with both in game gold and IRL currency. The fact that you can multiplay with friends nearby is a nice touch, could be fun to play this with friends when you're hanging out at home. This is a fun game, and I recommend you give it a try.