Trekkan's got it right.
There are 5 possible levels of access, which I hoped made sense in my description...
Each one builds on the previous one, starting with...
None: no access at all. if they try to access the game, they get a no permission error.
View: users can go check out the game page where the tabs for scores, discussion, and stats are on the side, but unable to start the game up.
Play: users can run and play the game, but the forum basically ignores them doing this entirely
Record: when the user is done playing, the forum counts their time in the forum stats - score is ignored
Score: the forum records their score and they are eligible for trophies and such [some mochi games dont report the score]
This allows you to set up fun things like...
allowing guests to play in your arcade, but ignoring the stats and scoring (so they get Play) - although it will let you keep score under Guest!
only letting users View until they get a certain amount of posts, upon which they can Score, but if they play too much, its just down to Record
The permissions system lets you also do things like set a usergroup standard, a game standard, usergroup+game, or general (which is the one you cant delete).
Thanks to trekkan's suggestions, if you get None when theres requirements to meet for View or better, you get an error explaining what you are missing. If you get None on the general permission, there is an arcade closed phrase that gets used. The other two arcades each did two different halves of this kind of thing in many places at once, so this combines them all into one place where you would most likely use it (unless you want to go back to editing an individual game every time

)
Now, the permission system actually does not filter out anything on the arcade portal due to it being too much of a strain to check the big stack of permissions for every game it tries to show (because tales of users with thousands of games is common), but the category system can help you with that

and thats coming up next.