Thank you very much for playing and for the kind feedback! :)
The cloud interaction should actually work just like the fuel tank: click and hold the left mouse button, drag the cloud horizontally, then release to drop it. Did you perhaps play on another device (like mobile, which sadly isn't supported yet) or in a browser other than Firefox on Windows?
As for the main menu, I wanted the labels to match the style of the Start button, so I used the same button theme for everything. I agree that this makes them look clickable and can be a bit misleading.
I also agree that the game is still missing sound effects. That would've added a lot more to the experience.
Thank you again for taking the time to play my game and leave such thoughtful feedback! :)