Shoot-'Em-Up Construction Kit (SEUCK)
Sensible Software's 1987 tool that let anyone build a vertical shooter on the Commodore 64 without writing a line of code.
Published by Outlaw, a Palace Software label, SEUCK was effectively a game engine with editors bolted on: draw sprites and background tiles, lay out a scrolling level, script enemy attack paths and weapons, then save the lot as a standalone program. Amiga and Atari ST versions followed in 1989.
The limits were as obvious as the possibilities — everything came out as a scrolling shooter with the engine's fixed physics and scoring — which is why SEUCK games are recognisable from across the room. It spawned a scene anyway: thousands of home-made games circulated on floppies and magazine cover disks, and the community still runs competitions. Same idea that later gave us GameMaker.