Guard's Riddle Number Card Game Javascript HTML5 Applet

This is an intriguing, single player card game where the player is supposed to arrange the cards in a specific order that obeys the following rule: For any pair of cards that share the number n, there must be exactly n - 1 cards between the pair. Below shows a possible solution to the game where the numbers range from 1 to 4:  

A possible solution where for 1 - 4

The game itself allows the player to try different ranges of cards, from 1 -3 all the way to 1-8. The aim of this game is to encourage students to think critically, and to familiarise themselves with the act of counting numbers.