Normally, a $10 game that I spend under 3 hours on would need to be really good in order to get a thumbs-up from me, and NightSky is not a really good game. It's not bad as indie puzzle platformers go, don't get me wrong, but a lot of the levels feel like one-off proof-of-concept gimmicks. (Admittedly, I only played Normal and then enough of Alternative to realize that it was basically just the same levels reworked to be jerkish, for the most part.)
That said, the reason this is getting a thumbs up is basically just that it was full of neat gimmick levels and the art, sound, and level design really clicked with me as something neat. So, I dunno. It's not a glowing recommendation, more just a "buy it if you really like puzzle platformers, ridiculous vehicles, or the artstyle" recommendation.