Game is actually pretty good for the most part aside from some jank:
The Good:
Simple mechanics, simple controls
Gravity controls sand and you. And everything else is based on level design. And you've got some good level design going on here.
Some of the best (and most difficult) puzzles are in galaxy 1 when the levels are constrained simply by the falling sand and player position. They are what I think are the most entertaining puzzles.
Good one-screen design
Puzzles such as these work best if they are all presented on one-screen for the players to internalise and study how their inputs affect puzzle solutions.
To improve:
Artstyle feels inconsistent
You have this realistic background setting with somewhat abstract designs for the foreground and puzzle element. Then you have the somewhat realistic sand, followed by abstract arrows on them. Ultimately, it was very all-over-the-place and not really pleasing to the eye.
The font imo, should just be a single colour. The gradient makes it hard to read and weird on presentation.
Perhaps simplify most of the elements, specifically the background to be more unified in design, especially in relation to the player (perhaps the most abstract of them all).
Puzzles (Level Design) is poor on Galaxy 2
The spinning level comes to mind. It's not really fun and presents itself as more of a chore.
The 'lock' level also comes to mind as one of the poor level design.
General puzzle design on galaxy 2 also feels limited and not as fun. The new kind of sand that only falls sideways or vertically is a great iteration on the general sand, but is not as well designed.
Refer to your puzzles on Galaxy 1 for some of the better puzzle designs.
Somewhat inconsistent pacing of puzzle complexity
This is entering personal opinion territory where I feel like in Galaxy 1, level 5 is an adrupt spike in difficulty but everything else is relatively medium and well-paced.
But I wouldn't know. At least I'll let you know I spent the most time on level 5.
Well done and overall, everything flows generally good. Puzzle design simply needs a lot more work and feels way more rushed in galaxy 2.