C:/Program Files/mingw-w64/x86_64-8.1.0-win32-seh-rt_v6-rev0/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.1.0/../../../../x86_64-w64-mingw32/bin/ld.exe: i386 architecture of input file `pong.obj' is incompatible with i386:x86-64 output
C:/Program Files/mingw-w64/x86_64-8.1.0-win32-seh-rt_v6-rev0/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.1.0/../../../../x86_64-w64-mingw32/lib/../lib/libmingw32.a(lib64_libmingw32_a-crt0_c.o):crt0_c.c:(.text.startup+0x2e): undefined reference to `WinMain'
pong.obj:pong.asm:(code+0xf): undefined reference to `_MessageBoxA@16'
pong.obj:pong.asm:(code+0x16): undefined reference to `_ExitProcess@4'
collect2.exe: error: ld returned 1 exit status