Armored Core 4 is a radical departure from the previous games in both the way the game is played and presented especially with Miyazaki on his debut as the director. While customization isn't as deep as before, missions are short and the environments feel like a step behind, the moment-to-moment gameplay is really fun and felt like a step in the right direction as the series moved to a new generation. The satisfaction of completing a level is also complemented to the story, more notably the player mercenary/operator relationship developing as you finish each mission. The story was also nice and had some signs of greatness, but I feel like it could have elevated to something better if not for a few missteps. The soundtrack bangs as expected from an AC game. Definitely recommend this one and it also runs well on an emulator.

By the way, if you think this game is too easy, remember that the canon playthrough is the Hard mode and it changes the missions unlike AC2/3 where it only changed the size of the FCS.