Earth 2150 is a game of discovery, awe and wonder; like so many other RTS's you start out with the bare minimum of available units for construction and use. But soon it becomes apparent that through research you can get both new weapons, traction systems, armors, shields and aerial propulsion systems. The design of the units will thus in time, become up to the player, who will be able to make units for any situation and counter his enemy's units and weapons through clever research and construction.
Compared to most other RTS's the research and design adds a new element, not only will you be restricted to always see the same types of 8 units but you can diversify and your opponent will most likely have a different design for you to counter - or die trying.
Not only will you have to master the ground and they skies you'll also have to defend and attack underground, diggers allow you to dig tunnels all the way under your opponents base, allowing you to launch a surprise attack from underground.
The only bad thing about the game is it's camera which in the first game is not always intuitive, luckily the two latter games fixed this somewhat, still you don't get to see as much as you do in for instance Supreme Commander.
That said, the possibilities are virtually endless and the modding and multiplayer community is still very much alive to this day, giving you many hours of fun.