- In 1981 as I was a biochemistry student I took up a computing class, APL language on a IBM-370 mainframe. I used the skills a lot for my school work. I approached a teacher and got my first contract for a system that would let biochemistry students enter their lab measurements (on a decwriter terminal), and the output was neatly formatted tables of values on paper that they could cut and paste (literally) in their lab report, thus saving around 10 hours a week per student (thousands of tedious calculations you previously had to do by hand). I was hooked, and I was a hero (never had to pay for a beer after that).
The biochemistry department paid for the CPU time (quite expensive on a mainframe) for the system which ran for several years (I lost touch after I graduated). One day I noticed there was a local phone number for the mainframe in all major cities in the province. I got the idea of making a BBS for my group of friends, which was activated by secret menu options in my biochemistry system. My friends from all over the country were dialling in from their PC at home in terminal mode and exchanging messages.
Then we decided to program a dungeon game and plug it in the BBS. So now the multi-million-dollar mainframe, over expensive long-distance leased lines, was spewing forth such sage advice as "You are now in a long, dimly-lit hallway. The walls are made of huge stone blocks covered with wet mildew. Part of the North wall has crumbled. A skeleton lies near the boulders. There are exits at East, West and North. Enter your command:". After I graduated, I ported the BBS and the game to an IBM AT-286 PC at my new place of work, which was plugged into a modem. Nor more free long-distance though. It went on for years.
- In 1984 I bought a Commodore 64 and discovered BASIC, assembler, color, sound, and video games. I did lots of crazy stuff with it (I still have it somewhere). In 1985 with a friend I made a tactics game (same rules as the Tactics II board game) that, for some reason, took place on the island of Grenada which had just been invaded by the US. Here's a screenshot (a picture I took of the C64 monitor at the time).
- C64 screenshot Show Spoiler
Now it doesn't look much, until you learn that the game was played against a distant opponent through a modem. There was, at the time, to my knowledge, no C64 game that did this. You played entirely using a joystick, moving the black frame to place and move units on land and in the water, attacking enemy units, etc. All those movements would be replicated on your opponent's screen. Pressing the F1 key would open a chat window.
- Right after DOOM came out (1993 I think) I started building custom levels for multiplay (via IPX network). I also had great fun modifying the official levels without the other player's knowledge and watching them fall into traps that weren't there the week before. Here's a screenshot of an arena I made. I'm not sure why it's so grainy, it's difficult to run DOOM on Windows XP.
- DOOM screenshot Show Spoiler
There was a graphical editor in DOS, it was about as friendly as Blender and crashed about every 11 minutes.
wait, no.. it was actually an IBM XT; not an AT. That was the slightly more ancient and slower version. I surely didn't create any game content on it though, seing how I was 7 or 8 at the time .. 
I might still have some pixel dabblings I did with paintbrush.exe though (the ancestor of Windows Paint, all running in a glorious black and white DOS interface). It just so happens that I got that computer's back from my parents house not too long ago.. I'll ought to open it one of these days, dust it off, and see if it'd still run.. It hasn't booted in something like 15 years though.. Hard drive might not be in a pretty condition.. 
as well as the candy one.. and the batman one.. and the hospital one.. and .. 
