Make every weapon and item useful.
Make beating the odds possible (as someone said above, a small squad with superior tactics should have some chance of beating a large one). Similarly, limit things somehow so that even a super-equipped team will have some kind of weakness (especially in multiplayer). The x-com 80-item limit is probably a decent example.
Make any AI cunning, or at least operate in an unfathomable way - the X-COM games, particularly the first, were great for this - even after a decade of playing, the exact effect your actions have, and the exact reasons for their movements are never clear. I suspect looking at the relevant code would show that it's actually extremely simple and nothing like as 'alien' as it looks, but the illusion is there.
Vary the objectives, or give multiple victory conditions, at least on some maps, to allow for suicide missions, pyrrhic victories and sabotage or assassinations even against enormous forces.
Great sound. Animation and graphics are going to be necessarily limited. You'll need variety or nondescript music (or none at all), and some very satisfying gunshots, explosions and death screams. Hearing sound cues in the darkness during the enemy turn can be handy and atmospheric, too.
Fragile soldiers. Even the hardest bastard in the world shouldn't be able to wander around without fear. Having to pump tens of rounds into enemies is no fun, except in rare circumstances in single player (eg: TFTD's lobstermen, and they have a weakness, and you can later turn the tables on them, making it worthwhile. In a short-term context though, they'd be infuriating, and in multiplayer no fun), and having to protect your soldiers should be of paramount importance.
Chryssalids.
unconsciousness, or crippling, or immobilisation of some kind - do you abandon your man, or risk another soldier to save him? Do you kill your enemy or try to injure him, making him bait? Do you finish him off, removing the threat, or save your time and ammunition, and interrogate or capture him?
Jagged Alliance style aiming - you can take a pot shot, or pump more time units into aiming - one more or five, it's up to you.
_________________ Lonely as a Mushroom Cloud
|