Reicast is a Sega Dreamcast emulator. It's an app that allows you to play your Dreamcast games on your computer or android phone. We've even baked in some magic to make things looks prettier than they did on the Dreamcast. Of course, not all games work, and the ones that do often have glitches

Reicast primarily aims for speed and to run on android. It is derived from the nullDC codebase. We work on it in our spare time, because we love working on complicated, headache-inducing projects. Development traces back to late 2003 and has been largely non-continuous.

Naturally, there are many other Dreamcast emulation projects, each with its own goals and priorities. Here's a non-exaustive list: Makaron, Demul, Redream, nullDC. If Reicast doesn't work for you, you may want to check these out.