Thank you for playing, yeah it definitely needs a little more explanation for some things, mental darkness only affects the endings (if it's high you get a bad ending even if the park is clean), it's like stress, the flower that drops that icon reduces the mental darkness so it doesn't get high.
The bench drains all your energy so probably you didn't have enough energy to clean the trash. Yeah, I didn't have time to add random events to make it less repetitive.
Thank you for your feedback!