Achievements

You can archieve certain achievements what you can follow at the Achievements window (3rd icon at the bottom). At the window, you can check out how many enemies you shall slay or how many things you shall do to reach them. By reaching an achievement you'll receive certain rewards (such as on the picture below), but while the energy usage is not balanced, you shall not waste too much effort into this, because gathering like 1-3 item requires 3 energy, still...

At v0.8 beta release the game got two achievement types:

Builder


 * These achievements require resource collecting and/or building upgrades.

Killer


 * Achievement gives you some gold and unusual rewards, e.g. Small spark attack.