Good puzzle. Not very difficult so its a good beginner puzzle. Just about every set of colours is arranged in a simple way that makes it fairly straight forward as to what needs to be done. There aren't any extra blocks that take extra thought as to how they are added to the puzzle. Out of place blocks would make it more difficult.
I think the time limit is unnecessary in this and probably most 1 move puzzles. One can view the board for however long they want after losing and then just restart and do it no problem. A time limit would be better suited for a multi move puzzle where its harder to predict the entire outcome of the puzzle.
Also less to do with your puzzle and more to do with the game design. I negated the time limit by solving the puzzle in my head while the game was on the screen with the win and loss conditions. The timer doesn't run when on that screen but i can still see the puzzle in the background. Took about 30 seconds to arrange the blocks and win after that.