Theoretically, the shortest possible ladder with four-letter words, and no matching letters, is 5 steps. How close can you get to this?

Hardest four-letter ladder

After finding this ladder I wondered whether I could search for the hardest possible four-letter ladder; in other words, the pair of words that requires the largest number of steps. My first attempt at writing a program to do this, using the PAPG word database, was going to take something like 4000 hours to check all possible ladders, which didn't seem feasible.

After making a few assumptions to reduce the number of words I was testing I managed to get this down to under an hour.

Here's the nicest maximal word ladder I found:

If only AMEW or ANEN were valid words it would be possible to solve this in a three-step ladder. I warn you: this is a hard one! However, none of the words in the ladder are obscure.

Hardest three-letter ladder

If you want to warm up on something a lot easier, here's one of the longest word ladders I found with three-letter words:

The answers

Here are the answers:

anew to amen – 17 steps:

anew knew know snow show shod shed seed deed dyed dyes eyes eves even oven omen amen

ivy to end – 8 steps:

ivy icy ice ace act ant and end

Dots (Tochki)

Dots seems to have been invented in Russian universities when the Japanese game of Go was becoming popular, and it was developed as an adaptation that could be played on paper when no Go equipment was available.

The aim is to surround and capture one or more of your opponent's dots by making a continuous chain of your dots, but unlike in Go, no dots are removed from the board. The winner is the one who has captured the most dots of their opponent's.

Virus War (Voyna Virusov)

Virus War simulates a competition between two growing colonies of viruses. Each player has three moves in a row, and each move can consist either of adding one of their own viruses to the grid, or of killing an opponent's virus by shading it in their own colour.

An interesting feature of the game is that each player's viruses can spread through any viruses of their opponent that they've killed, but they are blocked by any of their own viruses that have been killed by the opponent.