I'm familiar with how short Nifflas's games usually are, but I guess I've been hoping that they would start being longer, for two reasons: 1, that he started charging for them, and 2, that he's moved away from pixel art. I know pixel art is very time-consuming, and when he started using photos for backgrounds instead I thought, that's too bad because I love Nifflas's pixel art, but at least this would free up some time for him to make the games bigger/longer with more areas. When Saira was released I was pretty surprised at how short it was, considering its price and the use of photos for graphics. But I guess I was still holding out hope that NightSky would be a longer game, since it was so long in development, and again, didn't require making pixel art for each area. (Now that I'm playing it I'm actually even surprised at how few photos there are so far. It's mostly just gradients and black foreground. I thought a couple years ago Nifflas said he was collecting tons of photos for use in this game.)
Back on topic, now that I've played the first few areas of the game I agree with those who suggest playing the normal game first and then the alternative version second. This gives you incentive to play the game twice, first for the atmosphere, and then for really hard puzzles. I agree with those who say that playing the hard version first will make the normal version seem boring and therefore it won't encourage playing twice.