The 12th issue of the Transactions on Computational Science journal, edited by Alexei Sourin and Olga Sourina, is devoted to the topic of cyberworlds. The 13 papers in the volume constitute revised and extended versions of a selection of contributions presented at CW 2010, the 20th International Conference on Cyberworlds, held in Singapore in October 2010. The selected papers span the areas of tangible interfaces, emotion recognition, haptic modeling, decision making under uncertainty, reliability measures, use of biometrics for avatar recognition, cybernavigation, multiuser virtual environments, spatial data sampling, web visualization, and interactive character animation system design.