I finished it and I have to adjust my score. The unfinished swan is well worth a 9. It kept getting better towards the end, and I found myself with a huge grin on my face at the beginning of the last chapter.
I didn't expect so much variety and novel ideas in just 1 little arcade game. I guess that's where the frustration comes from from certain reviewers, it definitely leaves you wanting more. Each idea could easily feature a full length puzzle game. There is a lot of variety in the art style as well, yet it all works together beautifully.
I took my time to explore and collect all the balloons. (Some were pretty hard to find) All together I spend about 6 hours to get to the end. A perfect length for me, not far of Portal's campaign. An awesome little gem, close to perfection except for some nasty slowdown in a few places.







