Oh wow, I am amazed that I was able to beat this without the walkthrough. It is extremely difficult, but beatable as I have found. It reminds me of Morningstar, which also involves decoding an ancient language. I had to use a walkthrough on Morningstar, but then I wished I had tried harder. So I was determined to figure this one out on my own.
I don't know why those specific items go on those specific slabs, but a sensible player will try placing the items on the slabs and then look around to see if anything has changed. The bottom of the cliff is an obvious place to look since it's a dead end. I realized there must be three items so I was able to figure out what the third item was because I had already found the other two in corresponding places. Once you figure out each slab is supposed to have a different item, you can find the right combination in a maximum of three tries. So RadCarrot is wrong because if you made the slab lower when you put the grass on it then the puzzle would be too easy. There are only three items so it becomes a simple matter of trying each of them and then if one of them instantly locks the slab into place you'd know too quickly, and by the third slab you'd only have one item left.
Then in the cave, there's only one place where you can do anything at first so naturally the player should use trial and error to find the right combination. Once he's tried all 8 of them and had nothing happen, he should then go through them all again but check the rest of the cave while each combination is in place. The door is an obvious place to check, although most players might assume that the door wouldn't open until all three other sections of the cave have been solved somehow. Also, once they get through the door they might assume that those other two places were just clues that were meant to help solve the door puzzle which they just solved by trial and error, so they may be reluctant to go back into the main room later. Luckily, I had a hunch the main room wasn't finished.
The next room in the cave was the part of the game that tempted me most to use the walkthrough. I could see there were 256 possible combinations for the red button and the blue button, which made me very reluctant to use trial and error this time. Thus I agonized over how to interpret the bizarre clues on the walls. Ten circles? But there are only two rows of eight transforming stones for a total of eight stones. I eventually realized that all ten circles must apply to only one row of four, since there are two sets of ten circles after all. It was pretty clear that the pattern on the left wall applied to the left row of stones and the pattern on the right applied to the row of stones on the right. The weird kanji-like symbols didn't make any sense to me so I thought it best to focus on the chains of circles. Why ten? And why were they linked together with either one line or four? Finally I realized that each wall had exactly three four-line links, which divided the circles into four groups. Those groups must correspond to the stones because there are four of each, I reasoned. And so the shapes of the stones must correspond to the numbers one through four. The only question that remained was which end of the circle chain was the left end and which end was the right end. Since there were only two choices for each chain, I was at a point where I could just use trial and error to figure out the rest.
After seeing nothing happen, it was a simple matter of remembering the red and blue lights in the other room and noticing that the two buttons next to the stones are red and blue as well. So I returned to look at the lights, retrieved the colored stones and proceeded to try using them everywhere.
Tricky game indeed.