Hey, so I'll explain some mechanics and tricks here that would be difficult to figure out without looking at the source code. Think it would be unfair if I'd keep these secrets ;)

The randomizer for new tiles follows certain rules:

• when the new crytal bag is empty, fill it with 1 crystal of each color
• then delete a crystal from the bag (must be different color than the crystal deleted last bag)
• draws crystals from the bag until empty

The starting RNG is rigged in your favor so that you can always grow the center crystal on move 2 or 4.

I think those rules are equivalent to "when the crystal bag has exactly one crystal left, reset it to 1 crystal of each of the 5 colors".

So there's essentially a hidden 6th preview slot (the bag), with an undetermined yet not completely random color. As crystals are drawn, their color is crossed off. The number of possible colors that the next crystal can be always cycles from 5 to 2 and then resets.

This wouldn't be much fun to track by hand, but it might be nice to have a subtle little indicator somewhere - probably just one (lit or unlit) pixel of each color. Though I don't often look more than 3 moves ahead anyway...

Well, the difference is that a different color is missing from the bag each time, which means you won't get bags missing the same color twice in a row. There is a very subtle indicator on the top of the frame but I don't really want anyone to count RNG bags much (as you said, not fun to track).

I actually don't really like that it's possible to deduce the final color, though it's kinda similar in Tetris which also utilizes a bag system (different there because you don't have unlimited time to place pieces).

The only thing I sometimes do during play is deduce 'bag breaks', when a color repeats in the preview I know that somewhere between those 2 draws, the bag was refilled.  So no constantly keeping track, just sometimes deducing on-the-fly.

Another fresh hint:

Sometimes it's best to bite the sour apple and use action to clear an area instead of placing a bunch of new crystals. A clean board can quickly deteriorate and end your run if you don't keep it tidy!

>Well, the difference is that a different color is missing from the bag each time

Oh right, I forgot about that. So one of the colors would have to be displayed differently-- with a dot, an underline, in the first position, etc.

>There is a very subtle indicator on the top of the frame

Cool, I'll look for that!

Hehe, if you ever manage to find & abuse the extra pixel let me know and I'll remove it ;)