

From 100 minutes of playing, the game runs perfectly, and has all of its functioning present.
The keys were mapped correctly but it detected the native keys as "Key 49" instead of "Z", etc. The bounds were easy to fix

Does not launch if more than one monitor is enabled
Disable every monitor but one and you'll be fine running native

Game boots expecting keyboard input by default so you have to either use the on screen keyboard or a bluetooth one to navigate the settings and set the game to detect controller input
Only issues I had with the game was that it doesn't support cloud saves and I had to use the on screen keyboard to set the input device in the settings, but otherwise I had a flawless experience. Game ran perfectly and I was getting a good 5-6 hours easy without changing tdp or anything. An easy recommend for games to play on deck.

I was honestly shocked at how easy it was to fix the one problem I had with this. It didn't load in a proper control scheme for it, and that took ten seconds. This is the Heroic version, so that makes sense. I had absolutely no issues after the initital setup.
works out of the box. native version
had to change from keyboard to controller on the options menu since it didn't automatically change when i launched the game.

Game refused to start on discrete Nvidia gpu with gpu offload, but works flawlessly on integrated AMD gpu.
Needed other sort of controls
MESA_LOADER_DRIVER_OVERRIDE=zink %command%
screen would not render on native nor on proton. forcing zink driver to run under vulkan instead of opengl worked on both proton and on native. (should also work on intel and nvidia)
Native version wouldn't open, had to force latest Proton to play.
Aside from that, game worked perfectly.

Key bindings needed to be set to play
Switch To Community Layout: Capy's Bindings
Switch To Community Layout
The game itself runs perfectly without any problems, though controls will need to be configured to intially navigate the menu.
Set face buttons to Z key and/or X key to initially navigate menus.
The game defaults to keyboard input with controller not readily working. Menus cannot be navigated unless keyboard is mapped to gamepad. Controller needs to be activated and configured in game options.

Some tinkering needed for gamepad use.
You will need to set a binding to the Escape key. I set mine to left trackpad click.
Tudo ok, não vi diferença entre a versão nativa e com proton
Para usar o controle do "xbox one" é preciso configurar no próprio jogo, não reconhece automaticamente.
Cave Story+ has no gamepad support out of the box. Use a community controller config, and you'll be good to go.
Default Controls aren't correct. You need to set them up yourself or Download a Community Layout. I used capy's Bindings.
Nothing more to say!
Game runs on Proton Experimental. I haven't tried any of the older versions to check.
Use Proton 5.0.10, native version or later versions crash on startup
Crashed on startup until I used the correct Proton version
So, this was be a pretty terrible out-of-box experience, but once it ran it was fine. It would crash on startup every time, and I had to try every proton version until I landed on the correct one (5.0.10).
Native port is a disgrace, use Proton instead
Sometimes a select few sprites in the game would get messed up when activating the Steam Overlay. The game needs restarted to fix this.
The native port has so many crashes, no controller support, fullscreen is broken if you have more than one monitor, it's just an all around disgrace. While Cave Story+ isn't a great port in general, it works a heck of a lot better running under Proton and I played for about 30 minutes. The only issues I encountered were related to the Steam Overlay breaking some sprites, but that's it (so far).
- Tested with a Steam Controller. Controller prompts for Cave Story+ are very generic, using terms like "Button 01". The controller will show up as "Gamepad 01", which I initially thought was an issue with Proton but it turns out it's just how the game is.
- Tested windowed and fullscreen and it actually worked
- Sound still dampens when you tab out, so that nifty feature still works.

Works perfectly.
I originally tried this in Proton because the native version had issues with my dual-monitor setup. Running it in Proton resolves this issue.