This paper introduces the controlled natural language PENG Light together with a language processor that is based on a bidirectional grammar. The language processor has the following interesting properties: (a) it translates declarative sentences written in PENG Light into a first-order logic notation (TPTP); (b) it generates declarative sentences in PENG Light taking syntactically annotated TPTP formulas as input; and (c) it translates questions written in PENG Light into (conjunctive) queries in TPTP notation and uses the TPTP representation of the query as a starting point for generating answers in PENG Light. Moreover, the controlled natural language processor can be interfaced directly with an automated reasoner in order to resolve anaphoric references and to answer questions stated in PENG Light. Key words: Controlled Natural Languages, Grammar Engineering, HumanComputer Interfaces, Knowledge Representation, Question Answering