I think you have so much room to expand what you have created so far. The turtle world you have created look great. I love the feedback sound affect when something is ready to go however, I don't feel compelled to explore as the first upgrade you are prompted with take 5 mins of just straight clicking to get or 5 mins of running between cloud dumps to get a pair of wings. Maybe adding in collection cap, so you can collect up to 20 or so of each item with room to upgrade that cap. This way you have about 100 seconds to roam around before you feel the need to come back. I know this sound like overkill, but I would greatly reduce the time lock on anything you put in for the first 15 or so mins of game play so that players get a feel for the game and get invested before you time lock things.
I first three times I played I spawned in the water under the turtle so I had no idea I was at the home base. I saw all of the stuff ahead of me and took off. I'm not sure if you are going for a make your own fun kind of vibe or knowledge based mechanic or not, but this could stand to have a bit of a tutorial as I immediately took off in the other direction to the other island without any knowledge of my space. I'm not sure if this my screen's resolution issues or not but the buttons at the bottom are barely noticeable since they are half cut off for me. I click on the first one and realize it takes you home, but because I had never been home in my mind so my thought was "how would I have ever found this on my own".
I also think making the world have more diegetic UI will make it play more smoothly. For example, instead of the popup UI for the rainbow/cloud collection just clicking the rainbow or hitting a button near the rainbow or once you get into a certain proximity will pick it up. This will at least speed up the collection so you don't have to go from wasd/arrrow to move mouse back to wasd/arrows. If there was more of a choice than pack this up or don't I would say the switch to the mouse is fine, but I'm doing arrows with my right hand and mouse with my right hand so there's a lot of back and forth for me.