The first Iron Marines is easily an all-time classic for me. Ironhide Studios took their years of experience as premier tower-defense designers and made something more akin to Starcraft both in look and feel while being careful to keep things manageable using a touchscreen. In a lot of ways, Iron Marines Invasion is just more of this, which is nice, but it feels less inspired this time around. It's good, but not special like the first game was.
Just like its predecessor, Iron Marines Invasion is a real-time strategy game where you tap and drag space marines, aliens, mechs, and hero units around a map that you have an overhead view of. Your missions vary from level to level, but they all revolve around a galactic conflict presenting an existential threat to most space-faring life.
Your units will attack all on their own and even regenerate lost health over time, so a lot of the game revolves around combining units or building base defenses that work well in combination with your spacing so that you are able to defeat your foes without having your own forces destroyed.
Iron Marines Invasion is a more expansive campaign than the original game, with essentially twice as many levels that have you doing a lot more planet hopping to fight in new locales. While some of these levels--particularly a few setpieces toward the end--feel like the pinnacle of Ironhide's RTS design capabilities to date, large sections of the game simply feel like a re-hash of the first Iron Marines.
A big reason why this game feels so much like the first one is because the unit design isn't all that different from the original Iron Marines. While you can mix and match a greater variety of units that look different, you are still playing with all the same unit archetypes, and because you can equip different sets of units to play with per mission, some duplication in roles is present as well.
Perhaps the most noticeable (and unwelcome) changes between Iron Marines and Iron Marines Invasion occur outside of the levels themselves. The level navigation menu is a confusing sprawl of distant planets, constant prompts for turning on notifications pop up, the tech tree upgrade system has fewer ways to customize your progression through the game, and there are fewer hero characters and unit packs that come with the base game (while many more are available for additional purchase).
None of these affect the moment-to-moment action too much, and Iron Marines Invasion is not so difficult that you might feel the need to purchase units to complete the campaign, but it all leaves a pretty gross taste in my mouth. To be fair, the original Iron Marines has some of this (and has added more over time), but Iron Marines Invasion takes things further and thus it feels more detrimental to the experience.
The bottom line
Iron Marines Invasion provides a whole lot more Iron Marines levels to play, which is nice. That said, many ways in which this game tries to evolve past its original formula feel mostly inconsequential and the others just seem like a way to further monetize players who already have to buy in to the experience already. I am glad to have more high-quality RTS action on iOS, but don't love what I have to put up to do so here.