Where to begin
This is probably the best, or at least one of the best games I've played on NG. I love puzzle games, and gap monsters was a great game with plenty to do. Once you've finished all of the levels, you can go back and try to complete them in the least amount of moves to 'star' them. If you don't want to do that, you can create levels of your own and try and rate other peoples custom levels.
The level editor allows for endless creativity, and gap world is a stroke of genius. The rating system allows you to find a game suited to your play style, by allowing you to find the games rated most fun, most challenging, etc. Gap world even keeps track of your stats.
As for the puzzle mechanics itself, as far as I am aware the play style is unique, which makes for longer and more interesting gameplay and an overall better experience. The mosters are funny and really add something to the game.
For the reasons stated above, I give you 5/5 and 10/10.