Flow
Also said as In the zone, Flow channel, Flow state
The state of being fully absorbed in a task that stretches your ability without overwhelming it, so that time seems to pass differently. Mihaly Csikszentmihalyi described it from interviews and experience sampling, from 1975 onward.
It explains two different ways to lose a player: too hard, and they leave angry; too easy, and they leave bored. Skill grows, so difficulty has to grow too. The channel is a model and its edges have never been measured for any given game. Reviews find that balance between challenge and skill relates to flow only moderately.
Say it
“Players are bored by world two and overwhelmed by world four. Smooth the ramp: add one new enemy type per level, and raise speed only after the player clears a level without being hit.”
Where you’ve seen it
Tetris gets faster as you clear lines, which keeps the challenge rising with your skill. Jenova Chen built his 2006 thesis game flOw around the idea, letting players choose their own difficulty as they go.
Not to be confused with fun
Flow is one kind of engagement, and some people enjoy games without ever being in it. Calm games and social games can be a joy with hardly any challenge at all.