This is an EXCELLENT game. It is intelligent. It has secrets and puzzles that take the game play way beyond the 'retro platformer" that I expected.
It plays smooth and rewards exploration. I get the same rewarding enjoyment out of this game as I did when I played Portal. You feel accomplishment when a puzzle is solved or a secret is found. This is a game that makes you say, "Jeez, that's brilliant."
This game was £7 very well spent! I do suggest using a game pad when playing it as the game is designed to be played that way.