Aquaria is a beautful underwater game that feels very much like a mixture of Ecco the Dolphin and Super Metroid. If you're not familiar with the Metroidvania styele of game,s it involves avast, open world where the player is given, generally, very little direction of where to go, with the only obstacles being environments or passages thta the player cannot explore due to needing to unlock abilities, find items, leanr amgic, or what have you.
Aquaria does this through songs, which lets you transform into other forms giving you new abilities, like energy blasts, faster swimming, or the ability to project light into darkness. The world is larger than I expected, and comprised of several distinct areas that run the gamut from the Kelp Forest, to a Sunken City, to the Veil, which should be seen in game to be properly experienced. Luckily, the game lets you put down as many checkpoints as you want, to let you mark down places you can't quite get to yet, or areas you might want to come back to later. If you want to collect veeyrthing, you'll be backtracking quite a bit.
Music is a focal point in the game, and so it's not surprising that Aquaria has fantastic music. The graphics are pretty for what they are, and the bit of voice acting in the game is good as well. Most of the songs seem to ebe a variation of the game's main theme, which becomes a point touched on in the game's plot later.
The game has tons of optional content, areas, and bosses, which lets you find either new optional forms, new costumes for Naija, the adventurer, or simply little trinkets that sit in your home that make the place look nicer and sometimes add little creatures to the area. The little touches like thsis bring the game from being good to much better.
Combat gets very 'shmupy/bullet helly' at times, and sometimes boils down to chugging healing items (which are made through a very robust recipe and cooking system - actually pretty neat!) and blasting away as fast as your right mouse button will let you click.
If I had any qualms with the game, it's that it feels like the fast travel is just few and far enough between to where you do a lot of swimming around, but if you get good at wall-boost chaining (and you will) a lot of this is mitigated. There's also a few moments where how to proceed is not immediately apparent, and it's only after i tried everything that i realized what the hint telling me what to do was actually supposed to be. The game also runs off of a save-point system, with no checkpoints in between, so a feath can force you to replay a bit more of your previous progress than you might like. This isn't a huge issue typically, though there is one optional boss that's quite a trek from a save point to get to, and isn't very easy to top it off.
Finally, the last problem: The game ends on a huge cliffhanger, and we will never see a sequel, more than likely. Oh well.
Fantastic game, and I would heavily recommend it