# Simon Tatham's Portable Puzzle Collection

http://www.chiark.greenend.org.uk/~sgtatham/puzzles/

Anyone love this puzzle collection (35 puzzles, yay!) as much as I do?

You are given a grid of squares, some of which contain diagonal mirrors. Every square which is not a mirror must be filled with one of three types of undead monster: a ghost, a vampire, or a zombie

Vampires can be seen directly, but are invisible when reflected in mirrors. Ghosts are the opposite way round: they can be seen in mirrors, but are invisible when looked at directly. Zombies are visible by any means.

Around the edge of the grid are written numbers, which indicate how many monsters can be seen if you look into the grid along a row or column starting from that position. (The diagonal mirrors are reflective on both sides.) You are also told the total number of each type of monster in the grid.

This puzzle type was invented by David Millar, under the name ‘Haunted Mirror Maze’

This is a much older puzzle. For example, see Floyd’s Bumpershoot, which dates to the mid-1980’s:

http://www.kaser.com/fb.html

No, that’s more like a puzzle in the collection called “Black Box”. Black Box is from the 1970s.

Hey some of those are pretty neat.

I wonder what it says about me that my first thought was to wonder if they all had known (efficient, i.e. not just brute force) solution algorithms, and how hard they’d be to implement.

Arise!

Just wanted to let you know that this excellent collection of games is available for mobiles (Android, iPad/iPhone, Windows 8.1/10). It’s easily the game(s) I play the most in my phone. Free, no ads, lots of fun.

I was just googling simon tatham undead brute force and ended up here!

I always like the idea of Undead, but it stays unstarred in the android app because on this particular game when playing 7x7 normal or 7x7 tricky I always seem to end up in a position of having long runs that I basically have to brute force, and I don’t like doing that :(

I wanted to know if perhaps I’m missing some insight?

e.g. in this example, how do you solve that bottom left area without just brute forcing it all like a machine?

I don’t play undead much because of that. The problem is a design one - the number of each type of undead is a key element of the puzzle, but difficult to visualize and reason about - and as such in certain configurations you basically need to test possible permutations in a way that, for humans, isn’t very pleasant.