"Shovel Knight" runs on 400x240, though i think it may require manual modification to its scaling multiplier:
Set a custom screen size scaling modifier to achieve pixel-perfect scaling
Go to the configuration files location.
Open render.bin with your preferred text editor.
Change screenSizeMultiplier= into the desired value. Listed below are some examples of the highest values possible to retain pixel-perfect scaling for the specified display resolutions:
1366x768: X3F60E3E4, 300% scale
1920x1080: X3F555550, 400% scale
2560x1440: X3F700000, 600% scale
3840x2160: X3F555550, 900% scale
Save and close the file.
Notes
This solution does add black borders around the game to maintain the pixel-perfect scaling. Changing the in-game Screen Scale option will reset the custom value.
You can also calculate the desired value yourself:
As an example: for 1920x1080, 400 pixels width goes into this resolution 4.8 times, so we want 4x (400%) scaling to retain the highest possible pixel-perfect size, so 1600 pixels. 1600/1920 ≈ 0.833 (83.3% scale from the resolution selected in-game). Convert this value into IEEE-754 with this[url]https://www.h-schmidt.net/FloatConverter/IEEE754.html[/url], and you get 0x3f555555, which is used as the value.
I set it to: X3F800000 and it looks good. Try it if you'd like.
There may be a better way to achieve pixel perfect with this game, if you know one, please do share.