**There is no level 13.** The level 13 is in fact missing. That's because the number 13 is a bad luck number. Many times (especially in the US) people consciously avoid the number 13, because it is believed that it causes bad luck. This is the developer's choice and has nothing to do with the game itself. The game has 13 levels numbered from 1-14, excluding the level 13. Officially this is called [triskaidekaphobia][1]. [1]: https://en.wikipedia.org/wiki/Triskaidekaphobia