I try to make puzzles range all the way from easy to hard, and to leave many open at once.

If you're setting a game during the Cuban Missile Crisis, look through a library. find out what people were wearing, what other issues were in the news, how houses were furnished, what cars were being driven. Especially include things which now seem foreign.

I like to employ a form of repetition, in which the same elements recur but in different and unexpected ways. rather than being discarded as soon as they are understood or passed over.

What I would pay much more attention to are the few points where the player can inadvertently make a career decision. Most players end up back-tracking, though some actually enjoy this.

I try to make puzzles range all the way from easy to hard, and to leave many open at once.

This means keeping many trails open at once, inevitably requiring a fairly 'parallel' plot. This plot should be discovered rather than announced, so show, don't tell.

Players very widely disagree with me about what's hard and what's easy. and in a way, 'I won, but it was a fight' is the best compliment a game can receive.