Today's free entertainment: Mussel, an underwater shmup. At least I think it's set underwater. There are jellyfish-like creatures, and the "Mussel" of the game's title stands for "Minature Underwater Strange Squid Eradication Liner". That's good enough for me.
In a lot of ways, Mussel is a pretty standard side-scrolling shoot-'em-up. You kill enemies, avoid being hit and collect power-ups. But while it starts out quite sedate, it quickly builds in intensity. One specific enemy type shakes the screen and emits a violent-sounding pop when it dies—an excellent piece of sound design that makes them incredibly satisfying to kill. This, coupled with the way the game is synced to its chiptune soundtrack, means that despite Mussel's subdued pixel graphics, it still feels loud and brazen.
It's difficult, too. As you fire, your ship is pushed back slightly by the recoil. It means you can never fire and move forwards, and so you're extra vulnerable when attempting to collect a power-up. Throw in some erratic moving enemies and you've got plenty of ways to needlessly waste lives.
You can download Mussel for free on itch.io.