Is there an event for game open?

Just wondering if there was an event for game open.

No. Things like Awake() and Start() exist for scripts, and there would be absolutely no sense to have a function that triggers on game close.

Actually, there is - and they are very handy for knowing when the user is in or out of the app. This is especially useful if you are on mobile (tell whether or not the user is ‘tabbed into’ your app) or when you have a windowed game and want to know if the user is inside that app.

Check out these references in the API documentation:

OnApplicationPause - Know when the user presses the home button on a mobile phone - great for storing time and applying progress based on the time elapsed once you get OnApplicationPause(false) which means the user is tabbed back into the app.

OnApplicationFocus - Similar to OnApplicationPause, this is more targeted towards desktop games - and triggers with a true/false if you tab out of a game with ALT+TAB or the like.

OnApplicationQuit - A great time to call things like PlayerPrefs.Save()