He is known for co-founding Westwood Studios, designing the PC game Blade Runner, and collaborating with Steven Spielberg on the Boom Blox and Boom Blox Bash Party video games for the Wii console based on Spielberg's design ideas.

[8] After InstantAction was shut down in November 2010, Castle went on to become Senior Advisor for Premium FanPage in January 2011,[9] and later joined Zynga as VP of Studios.

[10] Castle took a detour out of the video gaming industry to serve as Chief Strategy Officer for Shufflemaster (which became SHFL entertainment) in late 2011.

[11] He returned to video games as Creative Director for Kixeye's War Commander: Rogue Assault which launched worldwide in 2016.

[14] Castle was also given a BAFTA award (along with Steven Spielberg and Amir Rahimi) for his work on Boom Blox in 2009.