Largest architectural projection-mapped game

According to Official Guinness Records,

The largest architectural projection-mapped game is 2,218.65 m² (23,881 ft²) and was achieved by The Gadget Show (UK) at Excel London, UK on 18 November 2013.
The game itself was Namco's Pacman and was projected onto the Millennium Mills building, opposite the Excel, using six projectors.

For a complete list of 2013 records, please visit 2013 Guinness Records in United Kingdom.

Other United Kingdom records that might interest you:

• Largest collection of stamps featuring sea life
• Most consecutive film scores identified
• Largest ball of cling film/plastic wrap
• Most consecutive generations of twins
• Most star jumps carrying a 100 lb pack in one minute
• Fastest completion of Uncharted 3
• Most viewed online video advertisement
• Fasest speed for a boat driven blindfolded