I asked the same question. Unfortunately, what I was told was that they do not have them as they are working on them. If levels are confusing to let them know.
I am having trouble with many levels myself. I am spending upwards of an hour on each puzzle in some cases and I am becoming very frustrated. If I had the answer key, I was able to see it and then understand it. Currently, I am doing trial and error and it is not working well on the levels that are hard. I don't feel like I should be posting something daily in the forum to gain help, but I am almost there. Some of levels are very hard as I have no electronics background and this is the first experience with computer science for me in about 10 years!