I probably have to look into DeusEx, but when it was published some years ago, I didn't like the greyish and depressing levels.
I will see when I'll find time to play it. Thanks.

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Continuing The Tom Sawyer Experiment:

We could complexity by giving the ability to actually paint the fence controlled by the mouse while the game observes whether the player (or NPC) makes it accurately.

This extends the options:
Tom can paint the whole fence on his own without the help of the other children to atisfy aunt Polly. But, he didn't trade things from the others which could be useful in further levels of the game.
The other children can disturb him, means influence his ability to paint accurately, throwing things at him, or dirtening the fresh paint parts of the fence.
When another child paints the fence, Tom(the player) can observe how accurately it is. Tom can stop him, take the brush and show him how to paint and the game copies and saves the movements of the mouse, so that the child continues painting the fence in the way as Tom did it.
Imagine, that the childs painting can be influenced by the others or its mood (angry, bored or becoming lazy).

That's quite a bunch of complexity added, but this way it is like a sort of minigame within the game: painting.

If we program the action more general as an action that can be accurately depending on influences like disturbance and mood, than we can use it as a general ability of an npc within the whole game:
imagine ability
to build fences more or less accurately(which are more and less stabil),
to build houses and bridges(which are less and more reliable),
to fight more or less accurately (while the player can show with his mouse how to move the sword or how to switch from one to another enemy, and the npc copies it),
to drive a coach, to ride a horse ...

[to be continued, by anyone who likes to]