This topic is a collection of things that I think about this game. This does include spoilers and is meant as constructive critique from the perspective of a new player, it is not meant to pick fun of the developer but rather to help the developer to see this game from another angle.
Level 2
It's hard to judge the position of the cloned character, maybe add a circle shadow below him.
Level 3
The suggested solution to this level is to somehow set "platform" to the platform present in the scene, but the solution is to resize the editor window to skip the level. This is frustrating as the game suggests one thing, but you have to do another.
To get the bug on this level, you have to pan the camera to the bottom so you can see the text at the very top. I don't know which monitor the developer had, but on my monitor, which may have different specifications it was very difficult to read the text.
Level 4
I genuinely don't see how you would be able to get the bug.
The duck is incredibly frustrating to manipulate. Sometimes the duck would move faster than me on the slope which just restarted the level. Maybe increasing the friction of the object, changing the simulation body to a cube, and making the platforms bigger could help.
Level 5
This is just borderline torture. Playing with a keyboard just doesn't have the precision enough to align the characters facing direction with the duck. It would have been way better if the camera had to have the duck in view at all times.
Level 6
I really like games that make the player manipulate external data, but the player needs to be informed beforehand that this game expects you to do so. I had to look at another topic within this community to be able to find a solution.
I didn't know how to get the bug until I made another file named "bugsettings.txt" with "moving=true" within it. Clever.
Level 7
After getting used to what this game expects of me, I quickly found a solution to getting the bug. Turn off the sound in the settings. Again, clever.
Level 8
It is really confusing having to walk like this with the camera facing the bottom of the platforms and the collider info is really hard to see. It doesn't help that you can't take your time as there is a risk that a duck will strike you down.
There is no reference between the collider info tiles and the platform tiles, you just have to remember the relative position of each. Maybe it would have been better to have some kind of indexing system like chess or just put each collider info tile on each platform.
Every time the character moves, the camera moves a bit which I have to compensate with using my mouse, and each time the character dies the camera is rotated by about 90 degrees.
Level 9
The character is just way too slow to be able to avoid the ducks and the camera is so zoomed in it's hard to see where the ducks are going.
Level 10
Where is the bug?
Overall, I enjoyed most of these levels, most of the time but there were some times when I was just genuinely lost. With future tuning and better scope, I could see myself buying this game if it were further developed. Good job Robert :)