Fix cmake files and add input file

engine/CMakeLists.txt

@@ -9,6 +9,8 @@ set(CMAKE_CXX_STANDARD 20)
 set(SOURCES
     main.cpp
     main.h
+    input.cpp
+    input.h
     ${CMAKE_SOURCE_DIR}/include/glad.c
 )
 
@@ -26,15 +28,15 @@ if(WIN32)
         ${CMAKE_SOURCE_DIR}/lib/luajit.lib
     )
 elseif(UNIX)
-    include_directories(${SDL2_INCLUDE_DIRS} ${LUAJIT_INCLUDE_DIRS})
-    link_directories(${SDL2_LIBRARY_DIRS} ${LUAJIT_LIBRARY_DIRS})
+    find_package(SDL2 REQUIRED)
+
+    include_directories(${SDL2_INCLUDE_DIRS})
 
     target_link_libraries(engine
-        ${SDL2_LIBRARIES}
-        ${LUAJIT_LIBRARIES}
+        SDL2::SDL2
         luajit
-        dl  # just in case LuaJIT needs dynamic linking
-        m   # math lib, commonly needed
+        dl
+        m
     )
 endif()