Peg Jump: a primer on sequential removal puzzles

Continuing my survey of sequential movement puzzles in the app store, I will take up sequential removal puzzles in the next few posts. In a sequential removal puzzle, pieces are removed one after another until a particular goal is met, typically the removal of all pieces, or all but one. All sequential movement puzzles, including sequential removal puzzles, can be considered to be mazes, including classic sliding block puzzles and more fancy “hidden” multi-state mazes.

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Set: another copyright problem

The game Set (designed by Marsha Falko in 1991) is a very enjoyable and innovative card game, in which the object is to find matching sets of three cards as quickly as possible. The deck of cards consists of 81 cards that are all unique combinations of four characteristics with three different options (3 to the power 4 = 81). For example, in the picture shown to the right, the characteristics are color, shape, shadings, and number of objects. The company Mustang Mobile (run by the Falko family) has the exclusive license for development of mobile versions of this game, but this company has (not yet) released a version for the iPhone. However, their exclusive license does not withhold others to do this (a recurrent problem). The following apps are straightforward implementations of Set for the iPhone (links redirect to iTunes):

Please acknowledge the designer!

The point of copyright and intellectual property for puzzle designs already came up in passing in my posts about to Rush Hour and Lunar Lockout. However, today an even more obvious problem arose in the app store: Blockade (link redirects to iTunes). This gives me the possibility to very clearly and forcefully explain to all developers out there:  

• Puzzle-designs are intellectual property of the designer.
• Even if they are available online, please ask the designer when you want to use the puzzle.
  
• Don’t be afraid: most will be thrilled and extremely cooperative.
  
• And most importantly: mention the name of the designer clearly alongside each individual puzzle!

Knight’s jump mazes: nothing really there yet

By using special rules for movement, simple mazes can become complex multi-state maze-puzzles. A well-known special kind of movement that can be used for such puzzles is the knight’s jump from chess. There are two puzzles available in the app store that use this kind of movement, but neither of them offers really nice puzzles yet. However, this could easily be changed for the better.

Tilt mazes: replacing dexterity with logic

One of the fascinating possibilities of the iPhone is to use the accelerometer to guide objects through mazes. This can be done with mazes in a literal sense, like in Labyrinth, or in a somewhat less maze-like setting, as in Super Monkey Ball. In these apps, the problems have to be solved through dexterity: a steady hand and smooth movements are necessary reach the goal.

In contrast, the principle of tilt mazes is to only use logic to reach the goal. The basic idea of such mazes is that the maze can be tilted, but the movements of all objects in the maze continue in the direction of the tilt until a wall (or hole) blocks the movement. As far as I know, Andrea Gilbert was the first to propose such puzzles in 1999.

There are three implementations available in the app store that use this principle (links redirect to iTunes):

Riddle racing until blocked

In my previous post I discussed various puzzles that used the principle of “movement-until-blocked” to transform a simple grid into a more or less complex maze. In a comment to that post, Bob Hearn drew my attention to another such puzzle in the app store that I had missed (iTunes link): Riddle Racer (a free version to try it out is also available). The goal of this puzzle is to move the car to the centre of the board with the help of the orange pylons. Both the car and the pylons can be moved, but only if they are blocked at some point by the car or another pylon.

Movement-until-blocked mazes

A regular maze is good, but a concealed maze is better. By allowing only particular kinds of movements, a simple grid suddenly can become a twisted virtual maze. A recurrent trick is to only allow straight movement that continues until blocked. Various puzzles in the app store use this approach. And to give away my conclusion, I find Q Touch (shown here to the right) currently the most interesting of them.

The following five apps all are this kind of “movement-until-blocked” mazes:

KinWits: more multi-state by paired movement

One of the ways to make ‘virtual’ multi-state mazes is by using multiple moving figures. You will be in different parts of the maze depending on the combined position of all moving figures. I discussed a particularly nice example of such mazes in my previous post on Theseus. However, there is another puzzle of this kind in the app store: KinWits (there is also a free version of this puzzle to try it out). And if you wonder why this puzzle is a maze in the first place (it sure doesn’t look like one on face value), then read my primer on maze puzzles before you read the rest of this post.

Theseus: a multi-state maze by paired movement

If you can get hold of a copy of Robert Abbott’s books Mad Mazes and Super Mazes you should immediately buy them. Unfortunately, they are out of print now. These books really redefine what mazes are all about. They contain various ingenious variations on the multi-state theme: your position in the maze is actually different depending on how you got there. Although there are many ways to make such mazes (see for example my previous posts), Robert Abbott’s designs are as good as it can get. Now one of his multi-state maze designs (or ‘mazes with rules’ as he likes to call them) has hit the app store: Theseus (iTunes link).

How to get multi-state: a maze with funky doors

The basic idea of a multi-state maze is that a visually perceived position in the maze can have different ‘states’. This means that being in a particular position in (the visual presentation of) the maze does not mean that you are in the same position of the state-diagram of the maze. In other words: although it might seem that you are on the same position, you can be in different parts of the ‘real’ maze. This abstract principle needs to a good mechanism to work as a puzzle. One approach is to use doors that selectively block a particular part of the maze, and which can only be moved in certain positions. As always with multi-state maze-design, this approach was pioneered by Robert Abbott in his Sliding Door Mazes. A variation on this theme (though I think completely independently developed) is the iPhone game Space Trap, shown here to the left (iTunes link).

[Update 6 February 2009] Space Trap seems to have disappeared from the app store, but today another version of the same puzzling principle became available: Open Doors. Different developers, but there seems to be a direct connection between Alcomi (the company behind Space Trap) and Armor Games (from Open Doors). All a bit confusing though… [end update]

Thing that roll: Rolling Block puzzles

As argued in my previous post, maze puzzles get more interesting when the actual maze is concealed. A really nice concealment of a maze puzzle are rolling block puzzles. In such puzzles a block (larger than 1x1x1, typically 1x1x2) is rolled around a grid of squares. What is so special about that, you might ask? Well, the effect is a multi-state maze, which can result in really nice puzzles.