What toys teach designers
A ball has no win condition. Neither does a set of blocks, a kaleidoscope, a puddle or a swing. They hold attention anyway, sometimes for years, and they do it with almost no apparatus. Games, which have goals, scores, progressions and endings, sometimes hold attention less well with a great deal more machinery. That gap is worth examining.
The distinction is old and not especially sharp — children turn toys into games within minutes, and many games contain toys inside them. But keeping the two apart for the length of an argument is useful.
A toy responds immediately and proportionally
Push a swing harder and it goes higher, at once, by an amount you can feel. There is no delay, no threshold and no state in which the push does nothing. This is the property that games most often lose as they add systems: an input passes into a queue, gets modified by three modifiers and emerges as a number in a log.
It is not that indirection is wrong. It is that every step of indirection spends some of the connection between hand and world, and the budget is finite. Toys spend none of it, which is why a very simple toy can outlast a very complicated game.
A toy is honest about its limits
You can see what a set of blocks does. Nothing is hidden, nothing unlocks, and the boundary of the material is visible from the first minute. This turns out not to reduce interest, because the interest was never in discovering the boundary; it was in working inside it.
Design that leans hard on concealment — on the next unlock, the next reveal — is borrowing against a limited supply. Toys demonstrate that the supply is not required. A visible, complete set of possibilities can hold someone indefinitely if the possibilities recombine.
A toy lets you set the problem
The most important property. The child with blocks decides what is being attempted: a tower, a bridge, the tallest thing that survives being knocked. The toy supplies the material and the constraints; the goal comes from the person.
Games that feel generous usually leave some of this open. They provide a goal but do not object when you adopt another one, and they leave enough slack in the simulation for a self-set problem to be attemptable. Games that feel narrow are often mechanically rich but have arranged things so that only the stated goal is possible, which converts a world into a task list.
What this does not license
It does not follow that goals are a mistake or that open-ended design is superior. A goal is what makes tension possible, and tension is not available from blocks. The point is that toy-like properties are separable from goal structure and can be added to goal-driven work without weakening it: immediate response, visible limits, and slack for self-set problems.
The reverse also holds. A toy with no resistance becomes boring quickly, which is why the best of them have physics with real friction in them. Resistance is the toy's version of difficulty and it is doing the same job.
A practical test
Stand still in your own game and do nothing for thirty seconds. If the world does nothing back, you have built a task and not a place. Then take an action with no strategic purpose at all — the equivalent of throwing a ball at a wall — and see whether anything at all responds.
The answer to that second test is the toy content of the design, and it correlates unusually well with whether anyone plays a game after they have finished it.