One Letter app for iPhone and iPad

One Letter is a word game in which you make words by only changing One Letter of the current word. There are four game formats.

Chains
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The idea behind Chains is that you start with a word, then you have to keep changing a single letter making a new word until you cant make any more.

For example the starting word is START: start -> stare -> spare -> spore -> sport -> etc


Variations
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Variations follows a similar patter to Chains, you have to change a single letter to make a new word. The difference here is that all the words must be made from the starting word.

For example you start with the word START. From start you can make: stare, smart, stark, scart


Additions
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With additions you are presented with a 3 letter word, and you have to make as many four letter words as you can by adding One Letter. You can place the letter anywhere in the word.

For example starting with the word POT: spot, pout, plot, etc


Ladders
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Giving a starting word can you change it to the finish word one changing a single letter at a time?