As a game from 9 years ago, it's notable for successfully mixing 2D navigation with 3D graphics and detailed environments. It feels like a shooter and you do have to use tactics like bouncing grenades, hiding behind cover to reload, etc--the move set feels by-the-numbers but it's executed well. The story, in terms of spoken dialog, is not great, but you can tell there's some logic in how the facility fits together and the vibe is consistent.

I have mixed feelings about how aggressively streamlined it is, but I do respect it for staying out of the player's way and letting them play the thing. There's no walls of text here--contrast with Metroid Fusion (a great game that gets a little too talky sometimes).

The secrets don't feel like "secrets" so much as semi-optional things to do. The question's less "where can I find things" and more "how do I get the thing that's clearly marked here on my map"

Buuuut I guess it makes sense for a smaller-budget hi-fi game to not attempt level designs that guide the player along to the places they need to go while making them feel proud of every little discovery they make with no explicit instructions or non-diegetic callouts