: To make a new problem from the original one and to compare their solutions are promising activities to promote a learner to be aware of the structure of these problems. Especially for knowledge-rich problems like word problems in arithmetic, mathematics or physics, this awareness is very important to master the use of solution methods. To realize such exercises in physics, we have developed a computer-based learning environment that allows a learner to make a new problem by changing the original one and that diagnoses the problem change. Preliminary evaluation of the learning environment has also been reported.