To paraphrase the eight major component of enjoyment defined by Mihaly Csikszentmihaly (p.49 of his book Flow).
1) We have a chance of completing those tasks.
2) We must be able to concentrate on what we are doing.
3) The task has clear goals.
4) The task provides immediate feedback
5) We act with a deep but effortless involvement that removes worries and frustrations of our daily life from our awareness.
6) The task allows us to exercise a sense of control over our actions.
7) Loss of self-consciousness.
8) The sense of duration of time is altered; hours pass by in minutes, and minutes can stretch out to feel like hours.