Blast Em is a retro, arcade style, side-scrolling, procedurally generated, spaceship shooter. The game is very simple. The only control you have is to move your mouse. You don't even need to click to shoot, your ship will continually shoot as fast as it can.
From what I have seen, it consists of 1 level that gets progressively harder with only 3 power-ups. Coins drop when you kill enemies. Harder enemies will drop higher value coins. Your score is entirely based on how many coins you pick up. Power-ups are dropped at certain intervals and they cost a certain number of coins if you decide to pick them up. These points are deducted from your score. The power-ups will wear off after a certain time and you will have to pick them up again.
The game is very difficult and each run will probably last from 30 to 90 seconds. You only have 1 life and if you collide with any enemy or projectile, you will die. The difficulty is partly based on the sheer number of objects moving on the screen at the same time. Also, with so many objects on the sceen, you can sometimes mistake the enemy projectile for a coin if you are not paying close attention.
I would definetly recommend going in the options and completely turning off the screen shaking. With so much stuff moving on the screen at the same time, having the screen shake every time you kill an enemy makes it that much worse. It also messes with my eyes becuase it feels like my eyes are out of focus every time it shakes and that can really make you disoriented after staring at the screen for so long.
I would also recommend turning off mouse acceleration if your computer has it on.
If you are looking for a very simple, but difficult, retro/arcade style, side-scrolling, spaceship shooter, then I would recommend it, although I would not pay the current $3 price. I feel like this is the kind of game that should be free to play on a website like newgrounds. I got it as part of a bundle and I am happy with it for what I paid.
Edit: I barely gave this a thumbs up yesterday when I wrote this, but after playing it some more I have changed my mind. In the first 2 hours I played, I didn't experience the problem others complain about where you randomly die without getting hit by anything, but in the last hour it has happened at least 7 or 8 times. I also have come to the conclusion that this games high difficulty is not based on player skill, but on bad game design. I useually find difficult games fun, but this game is difficult for the wrong reasons.