Action Alien was previously known as The Alien Wasteland and was first announced at Greenlight at the beginning of 2015. At this time it had very similar graphics to this redux.
After Greenlight, graphics and gameplay of the game were changed. The game was featuring a single map and was released in the middle of 2015. This first release had some bugs which were found and widely exposed by some youtubers.
After public apologies, the bugs were fixed just a day after and despite the negative coverage from the big youtubers, the game continued to be updated. It was improved for almost 2 more years, receiving 5 additional maps, destructible environments, open world gameplay, survival mode, perks system, achievements, etc...
While making these updates, I received a legal notice from inXile, developer of the RPG "Wasteland 2" who were threatening me of legal action due to the use of the word "wasteland" in The Alien Wasteland.
Because of the trademark issue, I had to change the title from The Alien Wasteland to Action Alien, here is an announcement from this time with more details : http://steamcommunity.com/games/382080/announcements/detail/847051596233968460 Action Alien : Prelude is a redux aiming to bring back the initial gameplay and graphics of The Alien Wasteland from Greenlight, but improved with updates from Action Alien (destructible environments, bug fixes, achievements, etc...) and for a much smaller price.
Changes in gameplay of Action Alien: Prelude are
Ability to crouch
No more crates with unlimited ammunition but ammo boxes, medkits and grenades to find after each alien wave
Weapons are more powerful, accurate and are faster to reload