The rules of ZIRKEL are simple. Over time some new things are added, but it never gets too complex. All rules have one thing in common: they affect how much time a flame needs to travel to a given location. Since indirectly controlling the movement of those flames is key in ZIRKEL, the best source for difficulty is an interesting combination of these rules.
When you take a step back you can identify the several properties and rules from which the puzzles are composed:
Basic relative flame proximity
- Ring position
- flame position
- flame direction
This is the most basic layer: depending on how rings are positioned relative to each other, where their flames sit and where those flames are headed, the flames must travel a certain distance before they can meet.
Simple rule: when a ring is double the size, it takes twice as long for a flame to make one round.
There are three types of flames in the game: normal, slow (half the speed of normal) and fast (twice as fast as normal).
Changes of properties over time
Later some rings switch one or more properties with every round. The most extreme case is when a ring changes its position, the flame speed and flame direction with every round.
Sometimes rules neutralize each other. For example, if there is one ring with a slow flame and another ring twice as big with a normally paced flame, those flames need the same time to travel their ring.
There is one other phenomenon which is used in the fifth chapter („Cyclone“): rotation. Puzzles rotate around their center (and in some cases change the rotation speed or direction). But this does not affect the spatial relationships of the rings and flames to each other. It is simply a distraction, but one that works so well that I used it anyway.
So there is nothing random, every part of a puzzle is well thought. Can you solve them all?