According to the description on the developer's website, Earth Defenders HD was based on an minigame that they had previously created and, well, the classic Space Invaders. Intended for Windows, Android and, quite possibly, Mac as well, Earth Defenders HD looks to be an arcade-y shooter with elements of tower defense. As is always the case with such games, it looks there will be power-ups and improvements to unlock.

Official IndieDB page here.