The possible values for justify-content are only displayed on Levels 1 and 2. By Level 3 you're supposed to have all 5 values memorized even though you've only used 2 of them? I had to keep flipping back to Level 2 just to get a list of the possible values. For a game built for someone who has never used flex before, I think you're assuming too much familiarity with it.
I discovered this myself but it's not immediately obvious. I also found the final level to be overly difficult without a reference to all the css property names and values.
I agree with you about the last level. I definitely needed the "cheat sheets" as the options for properties are difficult to remember (names kind of blend together). Finally I opened another browser window on the site I could refer to. Then I was able to glean the right options and solve it without too much difficulty.
I too struggled on the last level, which was certainly jarring because the ramp up until that point was quite gentle.
That said, I did enjoy the last level as a challenge; it prompted me not only to review earlier levels, but also check documentation elsewhere. Much like a real-world challenge, these can be valuable learning experiences.
I thought that was intentional; the copy for levels 3 and 4 heavily hint at what the values should be. The learner is encouraged to try and guess.
This is similar to the way that https://rubymonk.com/ for example shows you how to do `2.even?` but doesn't show you the equivalent method for checking if a number is odd.
