In the days before photorealistic graphics, multi-terabyte hard disks and seemingly endless access to RAM, programmers had to come up with games that were innovative and challenging rather than merely beautiful. In the 1990s, one of the best-known was a text adventure game called Zork. No panning and zooming around video-quality worlds here - everything needed to be firmly installed in your imagination.
If you yearn for those days, or just want to see what they were like, there's a version of Zork running in a form that you can play online for free in your web browser. It's still all text-based, and it'll certainly make you think. About how to explore the online world it creates, and just how far technology has come.
See http://thcnet.net/zork/index.php to start playing.