The NP ratio tells you how many Neopoints you'll earn for every point you score while playing a game.
For example, if the NP ratio is 100 NP for every 150 game points scored, to earn the maximum 1,000 NP reward for playing, you'd have to score 1,500 points during the game.
On the other hand, if a game's NP ratio is 25 NP for every point scored, you'd only have to earn 40 points in the game to get the full 1,000 NP for playing.
Chemistry for Beginners:
You are in a very scary lab... in a very scary part of the Haunted Woods...
The object of the game is to build molecules from the atoms given to you. You only have a
limited number of atoms available, so place them carefully! Refer to the chart to see
which molecules can be built. When you reach the needed score for that level, you will
advance to the next level where more advanced molecules can be built. Avoid unstable
compounds - if you build one of them, or if you run out of atoms to build with, you lose
the game!