Sometimes, at the end of the day (or at the beginning), all you want to play on your mobile device is a brainless yet challenging game where you can just shoot things. The "Shoot Them Up" type of arcade games were hugely popular back in the day, and now several developers have been bringing them back for your blazing enjoyment. Son of Light is one of the newest in the block, and you can shoot them all up while traveling at the speed of light.
The mission for the game is pretty simple: you just need to shmup (STG or Shoot'em up) them all (we assume they're the enemies right?). In just one go, you get to face all the enemies and bosses that are coming at you, and you need to overcome them in a row, meaning you need to finish all 10 levels. Along the way, you get to face bonuses that will explode in your face (think pinatas, rainbows, etc).
You also get to change your ship's weapons, shields, lasers, guns, engines, etc, all the while setting it up to achieve your objectives, which is really just to kill them all. To unlock new kinds of weapons, you need to complete the missions on the side and collect crystals as well. If you want to reach the speed of light, you need to collect speed bonuses. Don't worry there are no galactic police to pull you over since there are no speed limits in this universe.
This type of game is also called bullet hell or danmaku, and it is pretty easy to figure out if you're a newcomer to this genre. And if you're a hardcore shmup type of person, then it will also present certain challenges. You can download Son of Light from the Google Play Store and there are in-app purchases available.