Answer: Rollercoaster Tycoon

Rollercoaster Tycoon is a construction management and simulation video game, released in 1999, that simulates the construction and management of an amusement park. The game, quite sophisticated for the time of its release, was coded entirely by programmer Chris Sawyer. Not only did Sawyer single-handedly create the game, but he did so using assembly language, a low-level programming language which is distinctly more difficult to work with than the high-level languages typically used in game creation.