TIL that 99% of RollerCoaster Tycoon was programmed in Assembly language and 1% was programmed in C by only one programmer in 2 years.

The famous game variants of RollerCoaster Tycoon that some of us might remember playing was surprisingly written all in Assembly language. Assembly language is a low level language. They use mnemonics to interact with machine codes and they aren't interactive or intuitive as today's high level languages. It's a commendable work to design a game with almost all of the code written using only mnemonics.

Here's a gameplay recording taken from youtube:

"The game was developed in a small village near Dunblane over the course of two years. Sawyer wrote 99% of the code for RollerCoaster Tycoon in x86 assembly language, with one percent of the functions written in C for interaction with the Windows operating system and DirectX. The graphics were made by artist Simon Foster using several 3D modeling, rendering, and paint programs such as LightWave 3D version 5.6, Raydream Studio version five, DeBabelizer Pro 4.5, Photoshop 5.5, PaintShop Pro version five, Deluxe Paint 2E, cosmigo Pro Motion version 4.2, Corel Painter version five, trueSpace version two, CorelDRAW 8, and Poser 4.
For his efforts, Sawyer received about $30 million of the estimated $180 million brought in by this game as well as Transport Tycoon and two other RollerCoaster Tycoon games."

Source - [Wikipedia article] (https://en.wikipedia.org/wiki/RollerCoaster_Tycoon)