Hi! Thank you for your feedbadk!
I made moving fast the default and only told the player in level 15 about the slow down feature as I wanted them to not use it until then, because of what you described. I would remove it from the page's controls but I don't want to because of transparency.
Also yeah! Level 7 has a pretty smart solution in plain sight.
EDIT: Also for the floral patterns, I used to make and study tweetcarts on twitter. One of them had a very similar effect to this, but I couldn't find it (it was posted a couple of years ago).
Ah I see. If you don't want users to use the feature until a certain point, it might be better to lock it off until that moment. At any rate I think it's fine having the slow-down feature -- I just think you need to know what experience you want to happen. If the player knows the slow-down feature, they are guaranteed to use it as it is fundamental to guaranteeing a successful play, and users don't want to replay a level if they have the option.
Great job!