I'm having a very difficult problem. I hope someone here can help. The problem is I am having trouble trying to remember what fun is in my game.

Here's how it goes. I have this awsome idea for a game. I think about various sections and ideas about the game and what it can do. In my mind, it is a very nice and fun game.

The problem? Making this cool idea into a real game. Coding requires looking up difficult problems and seeing solutions. Artwork requires using various manipulation layers. Scriptwork and sales requires a whole different set of problem. Music is entirelly different. Each one of these problems requires hours upon hours of hard and difficult work. Each one of them essential to making a good game. Yet, as I develop my game, I'm sort of reaching the crossroads where I'm asking myself, "is this game still fun?"

I don't know anymore. It's cool seeing your idea come to life but I don't know if the original idea I had is still fun after all the work in the middle. I don't know if what I created is what I orginally wanted or if what I orginally wanted was fun in the first place.

I keep wondering to myself "Sure, adding this feature and shading seem cool to develop but does it add to the fun of the game?"

I usually have problems like this. I don't make a game that I think will be fun to play but a game which is fun to make. Otherwise I end up getting bored and start procrastinating whilst coding a purposely fun game ;D

as I develop my game, I'm sort of reaching the crossroads where I'm asking myself, "is this game still fun?"
I don't know anymore. It's cool seeing your idea come to life but I don't know if the original idea I had is still fun after all the work in the middle. I don't know if what I created is what I orginally wanted or if what I orginally wanted was fun in the first place.
I keep wondering to myself "Sure, adding this feature and shading seem cool to develop but does it add to the fun of the game?"

It ought to be obvious: show it to people, get them to playtest it.
One little problem, though: getting good results from focus groups is an art, and if you are visibly present (and known to the test subjects to be the game's creator) the results will not be accurate.

I've experienced this myself over the past year. The realization that I had is that a really cool sounding idea doesn't always translate into a fun game. You must test the idea in a very basic form to get a feel if this is going to be fun or not. If it isn't fun you need to decide whether it simply needs some design tweaks or if the idea is bad as a whole and move on to the next idea.

Self testing games never works.
I've designed levels that I thought were fairly easy, while the folks who tried them told me they were insanely difficult.

I guess you need to find some folks online who are willing to spend time playing, and offer honest critiques ....

Pardon me, I'm but new here and I can't help listening in on this conversation.
Thought I'd drop in my five cents? Ahaha.

I'm not sure about it but if I remember, I think I used to read an interesting article somewhere about the mechanics of gameplay; and what makes it fun.
Ultimately what's fun for one may not be so for another, so I suppose you do have to keep your target audience in mind when developing such games.
Obviously, puzzle games may not be so fun for someone who'd rather get in on the action; who'd prefer to shoot stuff than to solve them.

That being said, just like the others have mentioned, the best way to know is to get people to play it. That's what betatesters are for.

Good luck!