Singapore maintains tight restrictions on arts and cultural performances. Most artistic works have to be vetted by the government in advance, and topics that breach so-called out of bounds markers (OB markers) are not permitted. While the OB markers are not publicly defined, they are generally assumed to include sensitive topics such as race, religion, and allegations of corruption or nepotism in government. Nudity and other forms of loosely defined "obscenity" are also banned. Singaporean film director Royston Tan has produced movies which challenge these policies, including a movie called Cut in reference to censorship of the arts.