One of their earliest titles was QS Defenda (originally QS Defender), a clone of the Defender arcade game for the ZX80 and ZX81 home computers. Greater success followed with later releases, including a Star Raiders-style game entitled Time-Gate which reached the top of the ZX Spectrum charts in December 1982.
The passage describes the early success of a company with their first game being a clone of Defender, followed by a more successful title that was inspired by Star Raiders and achieved high popularity on the ZX Spectrum.