Ladders to Learning - Explorers V - A Riddle Solved, Explanding Horizons (1984, McGraw-Hill Ryerson Ltd.). Photo from Commodore C64 GamebaseC64 GameBase Ladders_to_Learning_-_Explorers_V_-_A_Riddle_Solved,_Explanding_Horizons McGraw-Hill_Ryerson_Ltd. 1984