Very cool game, nice style for the pixel art and VERY NICE SFX and MUSIC!!!
The downloaded file comes with the source, so it can be compiled on linux, you just need the headers and to change the main function from int WINAPI WinMain(HINSTANCE, HINSTANCE, char*, int) to int main(), at the top of the file remove the #define USE_WINDOWS and replace it with #define USE_OPENAL, also fix the path for the #include "Extensions/olcPGEX_Sound.h".
While you’re at it, you can fix a bug in the game by going to line 261 and changing the if conditional statement so it looks like this:
lvl.id == 4 && lvl.level_state == LEVEL_COMPLETED
To compile it you will need openAL, apart from the standard PGE libraries, just run:
g++ -o coredefender main.cpp level.cpp enemy.cpp tower.cpp -lX11 -lGL -lpthread -lpng -lstdc++fs -std=c++17 -fpermissive -lopenal