idle.c

/*
	Change the number between the parentheses after APP_ID to the game you want to idle.
	Then run the program and when you're done idling press a key.
*/
//730 is the AppID for CSGO
//480 for Spacewar
#define APP_ID (730)

//Imported functions from libraries that are needed.

//Go to any installed steam game file directory and copy steam_api.dll from there into the same directory as this script.
//steam_api.dll
int SteamAPI_Init();
int SteamAPI_RestartAppIfNecessary(int id);

/* These two libraries should ship with your installation of Windows. */

//kernel32.dll
int SetEnvironmentVariableA(const char *name, const char *buffer);

//msvcrt.dll
int printf(const char *format, ...);
int getchar();
void exit(int status);
int sprintf(char *s, const char *format, ...);

int main()
{
	char szAppId[128];
	sprintf(szAppId, "%d", APP_ID);
	SetEnvironmentVariableA("SteamGameId", szAppId);
	SetEnvironmentVariableA("SteamAppId", szAppId);
	SteamAPI_Init();
	printf("Press any key to stop idling.\n");
	getchar();
	return 0;
}