OpenTTD

OpenTTD is one of the great open-source success stories of retro gaming: a from-scratch reimplementation of Chris Sawyer's 1994 classic Transport Tycoon Deluxe. Started in the early 2000s by a small volunteer team, it began by mimicking the original game's logic almost bit-for-bit, then kept going for two decades, growing into something far larger than the DOS title it was born from. You still build road, rail, air and sea networks to shuttle passengers, mail, coal and goods between towns and industries, racing the calendar and rival companies for profit.

What makes OpenTTD special is how it removed every limit the 1990s hardware imposed. Bigger maps, more vehicles, higher resolutions, multiplayer over the internet, and a huge ecosystem of downloadable content (NewGRFs) that swap in new trains, industries and climates. The signalling system in particular became deep enough to sustain an entire hobbyist community obsessed with efficient junction design. It runs natively on modern Windows, Linux and macOS while keeping that unmistakable isometric look.

As a game it holds up beautifully, largely because good economic-network design is timeless. Newcomers can enjoy a relaxed sandbox; veterans can min-max cargo flows for hours. It is also the model for how to preserve a beloved mechanic without emulation baggage: not a copy of the old executable, but a living continuation of the idea. For anyone who loved Transport Tycoon, this is where that itch is best scratched today.