Parasites from Uranus
About
In the bottom-left corner, you can see your money, the amount of power cells (essentially your lives), how many parasites you have killed, and buttons to start the next wave and buy a new turret.
Holding space speeds up time, for when parasites are far from your turrets. Parasites slow down as they are damaged, but will get a heal and a huge speed boost from picking up a power cell. Once a parasite makes it back to the spawn with a power cell, it is gone forever, and any parasite that makes it there and back takes some of your money with it.
When you buy a new turret, you must select a place. Turrets can only be purchased between waves, and the price will increase for every turret you own. You can; however, upgrade turrets in the middle of a wave, which can save you from losing.
Clicking on a turret displays it in the bottom-right corner, here you can see its stats, sell it, or upgrade it. The left upgrade usually upgrades the power and range, while downgrading the fire rate and money gain. The right upgrade usually does the opposite. A good balance between economy and damage is key to getting far.