Potato Graphics Option (get more fps)

Low framerate because you play on an actual potato? There's a literal potato option hidden away in a config file.

tl;dr for the real ones

Go to /Appdata/LocalLow/Little Flag Software, LLC/Neon White/<some number>/ and open prefs.dat
Change "potato": false, to "potato": true, and save (no need to make the file read-only).
ur game now looks like garbage (jk it's still pretty) and ur framerate is increased by a bunch. Probably. Get those red medals.

Super Secret Potato Mode (step by step)

There's a graphics option not available in-game that drastically improved the framerate for me. Maybe it'll help you, too.

Config File Location (prefs.dat)

The game stores various settings in a configuration file called prefs.dat inside AppData/LocalLow/Little Flag Software, LLC/Neon White/<some number>/.

Finding the folder on Windows
Open the start menu and type %appdata% in the search bar. You should see three sub-folders: "Local", "LocalLow", and "Roaming". (If you don't see these folders, you might have to go up one folder level, as %appdata% might have put you inside /AppData/Roaming already).
Open up the LocalLow folder, and then keep going into the Little Flag Software, LLC/Neon White/<some number>/ folder.
(This could be wrong as I'm running on linux, if the Little Flag Software, LLC folder isn't in LocalLow, try checking inside Roaming and Local instead.)

Finding the folder on Linux (via Proton)
You'll probably find prefs.dat inside your steam root > steamapps > compatdata folder. For me, it was in ~/.steam/steam/steamapps/compatdata/1533420/pfx/drive_c/users/steamuser/AppData/LocalLow/Little Flag Software, LLC/Neon White/<some number>/.

Secret Potato Option

Open up prefs.dat with any text editor. If it asks what program it should use to open the file, notepad will work just fine.
Inside prefs.dat, you'll find an option "potato": false, towards the bottom. Change the "false" to "true" (make sure you keep the rest of the line the same, including the comma). You could also change other options here like "crt", "aa", and "mainCameraAA", but I don't know if they have much effect.
Save the file. The potato option doesn't seem to get overwritten, so there's no need to make the file read only.

What does it do?

Makes the game look less pretty in exchange for a much faster framerate, in my experience. But we're here for speed, right?

[chaos_isnt_here]

Dude! you saved my game. It started crashing midway through and I couldnt get past the first 5 seconds of a lvl. I was thinking I'd have to upgrade my graphics card. Thanks!

[velvetworm]

Thanks for this! Surprisingly, I am running this on potato (I don't actually meet specs) AND on a mac using crossover.. I still get 30+ FPS except on one terrible level. This game is great

[日本語はできません]

I dont have a potato computer, but I feel like you are an un-sung hero for posting this

[Wii Sports Enjoyer]

side note, setting your FOV to higher than max yields some hilarious results

[Wii Sports Enjoyer]

underrated guide, thanks for posting