Rush Hour

One approach to make sliding block puzzles more complicated is by restricting the movements of the blocks. The most prominent example of this strategy is Rush Hour. In this puzzle, all sliding blocks are rectangles of size nx1. These blocks can only be moved in the direction of the elongation. The original trick to make this restriction transparent to the user is to show the block as cars (hence the name “Rush Hour”). It is then immediately obvious that the car can only be moved forwards or backwards, and not sideways.

Rush hour was invented by Nobuyuki “Nob” Yoshigahara and marketed as a physical puzzle by ThinkFun (formerly Binary Arts). There are at least four implementations of Rush Hour available in the app store (links redirect to iTunes):

• Blocked
• Gridlock
  
• ParkingLot
  
• PuzzleJam
  

Unfortunately, only Gridlock mentions the game’s origin in the splash text. All others simply describe it as a completely new puzzle, different from everything before. This is a particularly bad habit in the commercialization of puzzles. ThinkFun has apparently given the permission to redistribute Rush Hour (at least, one of the developers of the above implementations tells me so). However, this does not mean that it should be sold as a new idea!

Please, developers, could you properly acknowledge the original designer of a puzzle? At least mention a name, or, even better, contact the designer (if possible: Nob unfortunately died in 2004).

Various implementations as available in the app store move away from the car-centered theme, and simply show abstract blocks. Although visually gorgeous, I think these designs miss the central point of Nob’s original genius, namely to present the puzzle in a surrounding that makes it clear why some movements are not possible. For example, in the Blocked screenshot shown to the right, why would the blue block not be able to move down? Or in the PuzzleJam situation shown to the left, why would the green 2×1 block in the middle not be able to slide downwards?

Puzzle design is a tricky balance between good looks and intuitive presentation. The whole trick of a good puzzle is to come up with some strange restrictions to make the puzzle challenging. However, the more natural these strange restrictions are made to the user, the better the design.

[Update] A new implementation just became available, with isometric projection for nice looks: Traffic Jam 2. The “2” does not seem to have any reason, other than to suggest a mature product. I have never seen a version “1” of this game in the app store.

[Update 24 November 2008] I just can’t get enough, I just can’t get enough (sing along!). Today it is time to introduce TrafficJam. Different developer, different distributor, but same game, same title, same idea. What are these people thinking? Please stop it!

[Update 23 December 2008] This is probably the most fanciful Rush Hour variant: Trojan Horse. You have to move around conversing Greek soldiers and bundles of spears inside the Trojan horse to remove a crawling white soldier from the interior. Sound strange? It is! Though it is still Rush Hour at the inside—number seven in the app store.

[Update 30 December 2008] The developers of ParkingLot tried to ride on the christmas frenzy and released Santa’s ParkingLot. The only difference are the graphics, and they didn’t get better…

[Update 7 January 2009] Believe it or not, the new year brought nothing new: FreeParking. Further, I just realized that I completely have forgotten to mention here that Blockade (which I discussed in another post) also contains many Rush Hour puzzles (simply copied without credit from Nick Baxter’s Rush Hour page on the PuzzleWorld site).

[Update 16 January 2009] Let’s see how long these developers keep up with this weekly schedule. This week the name of the game is iTraffic Jam. Same as ever: no credits whatsoever. The next Rush Hour clone is due around 26 January.

[Update 23 February 2009] Well, it took a little more time than I had predicted, but here it is: the next Rush Hour clone: Pink Room. And, rejoice, the puzzle is introduced in the first sentence as “a sliding block puzzle invented by Nob Yoshigahara (known as Rush Hour or Traffic Jam).” That’s the way (aha aha) I like it!

[Update 8 March 2009] Next one: Blocked Car. Cute graphics though.

[Update 16 March 2009] With level editor included: Bottleneck’d.

[Update 20 March 2009] I don’t know how this name passed the reviewing process of the app store, but it did: Parking Lot (2-track software). It’s not the same implementation as ParkingLot. Though of course it is the same game…

[Update 2 April 2009] Even gold bars are used as an incentive to get people to buy this game: BoxOut.

[Update 4 April 2009] Blokt.

[Update 8 April 2009] iTrapped tries to extend Rush Hour by adding differently sized blocks, and blocks that have no movement restrictions. There is also a level editor included. Unfortunately, the movement restrictions are only indicated by shades of grey, which I find rather confusing. Also, with the dozen of apps offering great levels, who needs a level editor for hand-made Rush Hour puzzles?

[Update 26 April 2009] Block Hints is introduced as a game that is “like Blocked and Parking Lot”. Fine. But it is of course just a clone of Rush Hour!

[Update 18 May 2009] It’s not enough yet. Today brought us another version of Rush Hour: Unblock Me and Unblock Me FREE. Number 20. One day I’ll have to check though whether they are all still available.

[Update 4 June 2009] A new version: Blue Block. This one seems interesting, as it announces to provide 39963 levels [sic!], which is claimed to be all levels that need 20 or more moves. They are subdivided into several difficulty categories, so you can quickly jump to your favorite kind of level. Unfortunately though, from the screenshots provided it seems like you will not have free level choice within a difficulty level.

[Update 6 June 2009] Rush Hour using a Yachting theme: Yacht Puzzle and [FREE] Yacht Puzzle. And one using an Ambulance as the car to get out: Puzzled – Ambulance Challenge.

[Update 12 June 2009] The makers of Yacht Puzzle (see above) also published exactly the same puzzle with a different skin as Log Puzzle and [FREE] Log Puzzle. There seems to be one interesting aspect of this version, and that is that you have a choice which block you want to remove. I don’t really see the fun of this choice, but well…

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