Many of Sierra's most well known series began in the 1980s. In 1983, Sierra On-Line was contacted by IBM to create a game for the new PCjr. IBM offered to fund the entire development and marketing of the game, paying royalties. Ken and Roberta Williams accepted and started on the project. Roberta Williams created a story featuring classic fairy-tale elements. Her game concept includes animated color graphics, a pseudo 3D-perspective where the main character is visible on the screen, a more competent text parser that understands advanced commands from the player, and music playing in the background through the PCjr sound hardware. For the game, a complete development system called Adventure Game Interpreter (AGI) was developed. In mid-1984, "King's Quest: Quest for the Crown" was released to much acclaim, beginning the "King's Quest" series.