Mask simulation tools are typically extremely complicated to learn and to use effectively. Therefore, providing access to a mask simulation tool over a wide area network (WAN) to multiple on-line users can be very cost effective. Specifically, in a network-based simulation server, multiple users can view the same mask image, simulations, and analysis results and provide real-time comments to each other as simulation and analysis are performed, thereby encouraging invaluable problem-solving dialogue among users. The user interface for this mask simulation tool can advantageously facilitate this dialogue. For example, the user interface can include an enter box for a user to enter a message and a talk box for capturing any message sent by any user of the simulation tool using the enter box.