GraphicsThe 3-D graphical representation of the game world is completely unnecessary: All gameplay mechanics are handled on a flat 2-D plane. The 3-D representation is just graphical eye-candy.
LevelsThe first 100 levels of Archipelagos were hand-created by the developers and have land and elements strategically placed. Every 5 of those first 100 levels are designed in a recognizable shape (the world, England, Mickey Mouse, a pig, the company logo, etc.) Every island after #100, however, is randomly generated using that island's number as a seed. Although the island gets generated randomly, it is the same island every time because the seed is the same every time, so each level on its own will always be the same.
Looking at the overhead map view, the randomly-generated islands after #100 appear to be "drawn" using a mixture of circles and rectangles; randomly-wandering "squiggly" lines are used both as land and an absence of land.
LocalizationThe premise of the original European release of Archipelagos is quite different than the USA release: The islands are supposedly occupied by petrified "souls of the ancients", and under control by aliens. To beat the alien obelisk, the player needs to free all the souls from the stones by destroying them. The trees infecting the land are supposedly infecting the land with the "blood of the ancients".
The gameplay is 100% identical -- it just has a different premise. This is yet another example of American "marketing localization": Changing the game slightly to be more appealing to American audiences. Another example of marketing localization can be found in the differences between the Captain Blood European and USA releases.
TechnologyThe programing was ahead of its time for PC games: Even on an 8086, it displayed 3/4 full-screen solid-filled 3-D graphics (no vectors) at a decent clip, usually at 5fps or higher. It also runs in 384K of RAM (only 256K if running in CGA). Finally, the internal game calculations are done on a timer, and screen updates on EGA and VGA-based video modes are limited by screen retrace; this allows the game to run on modern machines without the need of slowdown programs.
With such efficient code, the manual doesn't list any system requirements for the PC -- the game runs on nearly every PC ever produced.