An idea (not sure if it will work well) - how about uncovering fields with a "wave" rather than one by one? So instead of linear time, make it linear-by-distance time. First reveal the original tile, then its neighbours, then their neighbours, ... It should still feel pretty fluid, but faster.
If I understand correctly what you're describing, it's more or less what's happening now. But it may not look like it if you're on the beginner grid, and may only look good/better on the larger grids (either expert size, or custom with very large size).
But in short, when you uncover the first tile of this wave, at each frame I uncover only 1/60 of the total. So if you've uncovered 600 tiles, 10 should be uncovered on each frame, and it should be done in 1 second if your display is at 60FPS.
But if you uncover 60 tiles only, it will uncover 1 per frame, and that can look pretty bland. Could it be what you see? If that's the case, I believe (with a good 60% certainty!) that I mostly need to revisit the method when it's for a small number of tiles.
Yes, I'm on a small grid, so only see a "chain" of the boxes being uncovered one by one. It does feel pretty slow, even though I'm nowhere close to speed solving : - )
I've thought about what you said a bit more, and I think you meant it should accelerate with time?
In any case, I've just done that and deployed it. So if you refresh the page, the animation should - hopefully - be less bland. Feel free to let me know what you think.
