The two NeoGeo Pocket Metal Slug games are both much, much easier than the “proper” NeoGeo games in the series, and they’re also as much about platforming as running and shooting, which differs from the big versions too. They are, however, still both excellent on the tiny screen.
I’ve completed them both before (a few times, I expect), but I hadn’t remembered much from the actual levels. There are a couple where the layout is basically a maze, which was a bit annoying as I got lost and all the baddies respawn, and having to press pause to swap between gun and grenade was not ideal, but 1st Mission was a lot of fun.