For clarity, I'm currently thinking in terms of classic RPG style, namely JRPGs.

So I had this random idea where you start at the end and progress to the beginning of the game. You literally start by taking on the Boss of the game. But, you also start overpowered and can take him down relatively easy, even though the battle still feels epic.

Then, you go through the final level, losing experience. Then, you de-level and have to choose what abilities/powers to give up.

Furthermore, failing objectives in missions can have their consequences. For example, in the forward-progression of the dungeon, you found an uber sword in a treasure chest. Well, in the backward progression style, you have to put that uber sword in the treasure chest. Exiting the dungeon without doing this will cost you experience points (of which you are warned about). The uber sword is going to be taken from you, regardless of whether you complete the objective or not.

I know, it's a silly idea, but maybe it could work. There's been a few films/tv shows (Seinfeild) that have managed to do this in a way that makes sense, so surely it can be done in a game...

I did a quick search and found someone else considering this idea, although it seems like you are de-leveling in a forward progression style:
http://www.escapistmagazine.com/articles/view/columns/extra-punctuation/8661-Extra-Punctuation-What-if-We-Leveled-Backwards

What about if all the character walk backwards too ?

Yep, it IS wonky, but the ultimate goal is de-level slower than the enemy de-levels, just like in a regular RPG you would want to level up faster than the enemy levels up.

But yes, the challenge is getting the reward to make sense. For example, in the Seinfeild example I mentioned above, story details revealed later in the show (earlier in the timeline) help make sense to elements that happened earlier. If it could reward you in that way that'd be neat.

Could be fun if it's a pretty short game, and the story has some nice "whoa"-moments.

You'd have to avoid fighting as much as possible since usually in an RPG you get exp by grinding monsters...

I'd definitely play something like this. It sounds awesome! I'd wonder how you would pull off the story so you understand that you're degressing back to square one (the end boss threw some magic spell on you, and you're doomed to un-peat history)?

Make it a Tuesday project!

Ever wonder what would happen in a game such as resident evil or metroid if the puzzles were designed to be solved backwards, and that should answer your problem.

Reminds me of Rolling Thunder III on the Sega Genesis/Megadrive, because on each mission you can pick a weapon from a stash of twelve, and the one you use in a mission can never be used again. This means that on game start you have lots of choice, and when you get to the end-game you are restricted to all the rotten stuff (unless you have saved the precious weapons for the end)

I like this idea!
A 'survival RPG' like described in that link is certainly more workable. You'd have to hide the player's HP, TP and item quantities (or not have them at all?) otherwise.

Really reversed, you could have some guy that heals you for a number of times at set points in the game. Some parts should be in normal order to avoid craziness, although craziness is good Consider dialogs, fights and dungeons. In a reversed dungeon the damage you receive for the whole dungeon/fight must be dictated, so perhaps you could add a little story/dialog/skit/cut-scene where the heroes lose health by obtaining a rare item otherwise (but again: how do you hide they will have had it in the first place?).
And in a reversed fight you could have moves that damage yourself too? Causing yourself to be healed at the beginning of the fight, means you hadn't had a fight before that, without healing.
(I would avoid reversed dialogs )

As a incentive you could have a set of alternatives beginnings instead of endings. For instance, there is a person that helps you maximally 5 times. If you need more help, other characters who can help you 5 times will be introduced. This helper person helps you out right in front of the final boss for the final fight, and dramatically loses his own life. If you do a crummy job, it turns out this person was a soldier you met at the end of your quest; but if you do a good job, it turns out this person was your father, who had helped you since the beginning.

I like the idea, but I can't imagine how it would actually turn out.
I just realised solving puzzles in reverse might be fun too But in some normal puzzles you can 'turn things back' if you made a mistake. Does that mean reverse puzzles need a 'turn things forward' feature My head hurts >.<

Someone's not been reading the original post.

Actually, you're both right. I've finished Braid though ...

I hadn't finished Braid yet...

Anyway, I'm somewhat intrigued by the backwards RPG idea. I'm trying to get my head wrapped around a way to make it work, but I haven't had any luck so far. I'm reasonably sure Onewing is smarter than me, though, so hopefully he can do better.

Sounds like a great idea. sound like you can build i nice story behind it as well. have some CGI showing a summary of how your got the diffrent powers.

make it so that you went to save girl that got kidnapped and taken to a maze like world. You folowed the kidnapper and manage to get help for some of the locals along the way that lent you some of their powers. But the power they lent you can only be in there realm and it is fading because they was apart of the boss and the boss is dead so the powers are fading.
So you kill the boss but on his death he is saying the portal is link to him an on his death it will close and you and the girl will be trapped in the world forever. So you are trying to make it back to the portal with the girl.
The girl has to be a healer though to make it a little easier.