Microgaming produced the first ever online casino back in 1994 and are UK based, or more precisely in the Isle Of Man. Their games are both licensed (like Jurassic Park) and proprietary for example Thunderstruck 2. They have produced more games than any other developer although many are ‘clones’ of each other! and they supply to multiplatform casinos through the Quickfire portal and of course their own download Viper client for Microgaming-only casinos. They specialize in 243-way games and are the most prolific provider of them.  The huge list of all Microgaming slots and RTP figures can be seen here.