Xghost, played on regular languages generated by regular expressions. Thus Superghost, Superduperghost, Xghost played on regular languages are all PSPACE-hard and in EXPSPACE. Spook on regular language is PSPACE-hard, but it's unknown if it's in EXPSPACE. In German In German, words can be formed quite freely by concatenation. Because of this, one can write a regular expression that generates a regular language L, such that every word in L is technically a word (which might be nonsensical) in German. A game of ghost played on such languages L is called German ghost. This variant was also shown to be PSPACE-hard. See also Unhalfbricking References Word games Solved games