Armed with Wings. The game that started the saga. And while the AwW universe is pretty solid, the very first its title didn't age that well. It is not simplistic, it is basic, though it has interesting counterattack feature, which is, sadly, kind of useless. We have our three-strike combo, uppercut slash and charged attack. Our eagle can fly around as long as it has enough stamina, and can also be left in wait anywhere to distract enemies, this feature is also rarely used.
For the new players this game will not be easy. The first boss is a major pain in the neck if you can't time your third strike properly and not sure what to do when it goes into "recovery" state.
Eagle labyrinth and stage 11 are also quite tedious levels, if you are not familiar with controls and timings.
Oh, you also can't jump (you can in Rearmed, however).
Also, what is the song in main menu? I think it is the only OST from AwW games I haven't found yet.