"Theme Park" took roughly a year and a half to develop. Much of the code was used in "Theme Hospital", and an animation editor was improved by "Theme Hospital"s designer and producer Mark Webley, who dubbed it The Complex Engine. Artist Gary Carr did not think the game was a good idea, and disliked the art style. Molyneux wanted him to create a colourful style to appeal to a Japanese market, but Carr disagreed and left Bullfrog. Carr later retracted his beliefs and, in 2012, stated that he considered the game a classic. In 1994, Molyneux was developing both "Theme Park" and "Magic Carpet". The game was mostly complete by January 1994 and scheduled for release on 28 March, but this was pushed back to June, and then August. "Theme Park" sold over 15 million copies, and was extremely popular in Japan (the Japanese PlayStation version sold 85 thousand copies within weeks), as well as Europe. "Theme Park" did not sell well in the United States; Molyneux hypothesised that this was because the graphics are too childish for American audiences. The game is the first instalment in Bullfrog's "Designer Series", and it was intended for the series to use "Theme Park"s engine and for each instalment to have three simulation levels. The PC version was sponsored by Midland Bank.