It is indeed raining!
These modifications allowed me to compile on windows fyi:
cmake_minimum_required(VERSION 3.23.1)
project(rain)
set(CMAKE_CXX_STANDARD 20)
if(NOT CMAKE_BUILD_TYPE)
set(CMAKE_BUILD_TYPE Release)
endif()
set(CMAKE_CXX_FLAGS "-Wall")
set(CMAKE_CXX_FLAGS_DEBUG "-g")
set(CMAKE_CXX_FLAGS_RELEASE "-O3")
add_executable(rain main.cpp)
find_package(OpenGL REQUIRED)
target_link_libraries(rain ${OPENGL_LIBRARIES})
file(COPY umbrella.png DESTINATION .)