mechanic vs theme start point

Personally. I go for mechanics first. I could ask the question in reverse ;)

I think that the best answer is to do simply what feels best at the moment.

Push forward with whatever strikes you at the moment.

Just recently I received critique about a game design that was primarily about the mechanics. The thematic elements emerged gradually, and at the time of testing weren't fully-realized.

One of the playtesters/reviewers remarked, "If it's not a theme-forward design, that's okay." He then explained that he would just expect to see interesting choices being the strength of the game instead.

Until he had mentioned it, I never was aware of the term "theme-forward." My assumption is that another game could be considered "mechanics-forward," like chess, go, or some of the games by Knizia. The theme could be tacked-on or deliberately abstracted.

So don't sweat it. Just keep working with it and through persistence the design strengths will emerge. The game will happen one way or another. :)

I start from either and then try to find the real center-piece which for me is the experience.

Like if I am wanting to make a light dungeon crawler, there are elements of the experience I want to focus on, like movement, discovery, and conflict. I'd find mechanics that allow for those and work through it. If that works, I could find a different setting, like exploring a forerunner relic location in space, or a temple.

If I start with just say tile laying, movement, and dice rolling it'd been much harder to find the fun. Sometmes, I'm in love with a mechanic like in another post I mentioned deck building with movement. From that I found a theme and a setting and identified the experience of improving your abilities to overcome progessive challenge scenarios to power the design.

What I mean is this: If my game is "Quest Adventure Cards(tm)" and I begin working on refining this design, I think about the elements that I would like to see if the game and that leads to mechanics and how it should come together...

So knowing what I want from the "experience" leads me to digging deeper with the "theme" and also what mechanics would work best with the game.

I also have a bunch of "pending" designs that I like to borrow elements from. See if I can piece together something "special". That too is also very important because when it works, in my experience it makes for a real good game. But sometimes I borrow a mechanic from another design and that leads me down another path for the design...

And so forth... iterative design.

I like to start with theme or rather concept idea and make everything tie into that core theme/concept it ensures that everything fits and feels like it should be there.

In my book "theme" is equal to the "type" of the game. If it's Quest AC, then it's Medieval Fantasy combined with Card Game Interaction. Because Quest AC was "primarily" a "card game" to begin with.

So working on a Second Edition - makes me think of similarities but the additional mechanics that are required to make a deeper experience. Quest AC was my FIRST "Published" game... And I've matured greatly as a Designer with "TradeWorlds".

So "theme" to me = "type of game" (Story, setting and interactivity).

Of course, inspiration comes from many sources, at any time. Why constrain yourself by only creating in one way? I also don't see why it doesn't happen both ways for most.

Have you never seen something in action (a possible mechanic) and thought of something that could fit it?

An example- I took a short walk the other day past a house that was getting an addition. As I walked by a worker threw some wood off the roof to the junk pile. The pieces hit & launched a few pieces in the pile into the air.
I have seen this happen thousands, if not millions, of times before. This time I saw it I thought 'not flea circus, but flea olympics to see whose flea can jump the highest'.