OliThink(5) is a free and open source chess engine, written in C.
One of the main aims was to create a strong engine with minimalistic and clear code. OliThink has no chess knowledge except mobility. The size of the source code is about 36kByte. There is no use of external libraries like endgame tablebases or neural net (NNUE). Everything in the code is unique, there is no copy of other engines. An independent invetion of Kindergarten Bitboards (2007) being used for move generation and mobility evaluation.
In order to play chess a chess GUI like xboard, cutechess, arena etc. is necessary. OliThink understands UCI since 5.11.9.
In this repository there is a history of sources and executables for Linux, MacOSX and Windows. OliThink has been translated into a Java engine. The Java engine is weaker but less than expected.