Solutions yes, but comments are visible in the homepage when not marked as having spoiler content. That's why you should use it here too.

Aren't solutions only visible to whoever unlocks solutions? Why do we need a spoiler flag in a page full of solutions?

Added.

According to the Ruby Style guide, the explicit return should be avoided here.

Thank you, phaul, for the explanation, that is very interesting!

Thank you for mentioning the optimization, bidouille!

I thought that solution feedback was visible only by those who already can see solutions…
Well, I won't forget next times.

Interesting solution! May I ask, how you arrived at this one and why the math adds up the way it does?

Use spoiler flag next time, please.

This is beautiful.