We consider a modeling language and a simulation environment based on object-oriented principles and aimed to help in the design of reactive systems. The language framework includes diagrams of object structure and interconnection, statecharts as a behavior description, and C-I+ for data objects and functions. Timed Transition Systems are used as a semantical model. COVERS enables the user to perform the whole modeling-simulation-analysis cycle within a single MS Windows-based graphical environment. We overview the code generation, model execution and visualization of results. The correspondence between COVERS language and the Unified notation is outlined.