This game has been designed at an introductory level. If, however, you would like students to have a reference point, direct them to view the quarter-past charts.
http://www.teachthis.com.au/products/view-resource/link/Quarter-Past-Charts/id/4052/
EXTENSIONS
Progress to "What's the Time Mr Wolf - Working with Quarters"
http://www.teachthis.com.au/products/view-resource/link/Whats-The-Time-Mr-Wolf-Quarter-To-and-Past/id/3728/