"mystery house" was released in 1980. it was a great success with 15,000 copies sold, earning 167,000 american dollars (equivalent to 525,539 american dollars in 2020). it is the first computer adventure game to have graphics, although made with crude, static, monochrome line drawings. the two decided to shift the company's focus to developing more graphical adventure games. "mystery house" became the first of their "hi-res adventure" series. the "hi-res adventure" series continued with "mission asteroid", which was released as "hi-res adventure #0" though being the second release. the next release, "wizard and the princess", also known as "adventure in serenia", is considered a prelude to the later "king's quest" series in both story and concept. through 1981 and 1982, more games were released in the series including "cranston manor", "ulysses and the golden fleece", "time zone", and "the dark crystal". a simplified version of "the dark crystal", intended for a younger audience, was written by al lowe and released as "gelfling adventure".