You can pick up the green thing that grows in some walls and use it as a temporary torch to light your way – this allows you to see the big wheel with numbers on it placed on a dark spot.

There are 2 types of light panels found in rooms and corridors – the ones with a button and the others that have a sliding panel on the left side with a lot of buttons that, once pressed, present the familiar star propagation pattern (used in the light everything kind of puzzles).

In the room with the paintings, there are at least 6 paintings you can pick and hang on the walls - the hang places I've found are: 4 close to the room entrance, 1 behind the incomplete painting and 1 on the right side of the same wall.

In the room with the instruments, the piano seems to be missing a crank (or something similar) since there’s a hotspot on the left side.

at the end of the small corridor behind the chair you can sit on.

Place the 4 "childish" looking paintings on the 4 spots close to the room entrance - if done correctly a sound will play and you cannot remove them anymore.

This gives you access to a diary with lots of pages to read probably with hints...

Once the four paintings are locked, look to the left in the pond. A rock slid open to revel a diary. Also, look closely at the paintings. There are numbers. Look closely at the centre of where the for paintings meet. Match the numbers to positions on the sliding rocks puzzle. The codes are on the pillars seen at the beginning of the game. These are light hints.

There's a total of 7 paintings in the room - it seems you've missed the one behind the door!

1: 551
2: 345
3: 462
4: 286
5: 873
6: 727
7: 134
8: 618

on the pillars located at the entrance of the game. After the bridge collapse.

I assume that the button in the workroom with fountain and star map will only work once all the lights are green, I assume this. The only other panel I see is at the end of a blocked corridor. Been looking for a way around the boulders but can not. I am guessing that a screen will come down for the stars to shine but I may be way off base here. I have checked every position of the wheel in the grotto. I checked every room and every hallway in each of the 24 positions to see if something somewhere that may have changed since it sounds like stone walls moving when the wheel is turned each time. Also been in the musical lookout but except for a drawing there doesn't seem to be anything there to do.

The color order is on the big wall painting that you moved the panes on to create the original picture. The white areas separate the colors so there could be the same color twice.

There are two buttons in the brothers work room that make the star chart drop down. They are located near the star chart too. Then if you ride up the tower in the music room you can see that contained in within the music note scribbles, there is one constellation. I have assumed that this is the one we're to be interested in. In particular, the opened circle as it "looks" like the symbol on the green/red light panels. I think we're to make that pattern in the light panel. As you have seen, there's one more light to be turned on and I too can't find it's location. Also, the button next to the book case activates the lever at the bottom of the stairs. When that is turned, you can see a walk way blade turn under the water.