This paper presents two design examples that illustrate instructional issues in the design and development of interactive computer simulations. The examples have been designed as exploratory tools that support a real activity for mining equipment operators. The first example, the Australian Conveyor Engineering simulator, was designed as not only a simulation tool, but also a sales and marketing tool. Simple, yet deceptive in its complexity, the conveyor simulator allows users to simulate the actions of a conveyor in a real-world underground environment. The user can adjust a wide range of options relating to the conveyor, and see the results (belt tension, power output of drive head etc) not only in mathematical and chart fonn. but alsot hrough a graphicalr epresentation,t he conveyor.C omponentsu nder stressr eactb y glowing yellow, then orange, then red. Users can test a given situation before actually implementing the design underground. The second example, the Joy Mining Machinery 12CM12 continuous miner simulator, has been designed to support operators in the initial phase of training for use of the continuous miner, where training on the job could be dangerous and lead to expensive losses. The simulator allows potential operators to perform all miner operations on-screen while using a multimedia training program. In an attempt to add more power to the simulation the program also incorporates a replica of the actual machine controls, so the user can operate the simulator not through a mouse and keyboard, but also use the actual controls.