it's a very nice concept, and i enjoyed the depth mechanic a lot, but i agree with other comments that the way it works is not very intuitive, so it took me a while to understand how to play. that's not necessarily a bad thing, but in case making us learn through trial and error was not your intention, maybe look into adding a brief explanation of how the depth mechanic works in relation to the orbs and their plants :)
i would also say that, despite advancing a lot further after i got a better grasp of the gameplay, i still got completely stuck at times after using one orb to travel forwards, then moving backwards after leaving it behind. it happened with the red orb - i moved with it then left it, forgetting it was what made it possible for me to move forwards, and when i moved back, i lost the orb and wasn't able to move again to get it back. it's also an issue in that area where you move forwards with the white orb and then fall into a red orb area. that resulted in me having to restart the game and lose all my progress (twice). i would definitely suggest adding an "undo" button to allow us players an easy fix for silly mistakes like that!
all that being said, i really loved the game, and the art is very pretty which is always a big plus!!
i really hope you continue working on this project, and i'm very happy that you chose to share it!!