Oh, I think I found a bug !
Minor spoiler below :
At the end, if you put the ceramic shard out of the little window, it disapears and it seems you're completely stuck !
This bug should be fixed in version 1.1 (I just tried in Windows and couldn't get rid of the shard) which was uploaded 24 days ago - is it possible you downloaded before that?
And thank you, happy you're enjoying the game! Do you want a hint for the secret ending or do you want to figure it out on your own?