JoeJ said:
The problem is: Running out of new mechanics, all we can do is extending classic and simple concepts with new mechanics like this. So we increase complexity with time, no matter if we really want or not. E.g. like currently with adding RPG mechanics to pretty much every game. That's a real dilemma to me. Making a science out of game design does not help, and seemingly makes it only worse.
That's part of a long-developed part of the science aspect of game design.
Consider two axes, one axis is width, the other is depth. You get wider the more features you add, feature A, feature B, feature C. You get deeper the more you can do with the feature, the more variation it provides.
If you implement a feature and it only does one thing, that's adding width but not increasing depth. You get a single command and a single action. Open an item, that's it. Swing a sword, that's it. You can add depth by making it do multiple things. For example, instead of just “swing a sword” you can get five or ten varieties of swing based on how you take the action.
A good example of this recently was the Zelda Tears of the Kingdom Fuse mechanic. Simple mechanic, fuse two items together. But it's very deep, there are lists with thousands of combinations. Many are boring and seemingly obvious: attach a spear to a spear and you get a spear with extra long reach. Some are a little weird, a fan on a shield can push away enemies, a spring on a shield can bounce them away, which gets interesting on ice. Bee honey on a sword or shield summons bees to help you, weird but whatever. Adding fire, ice, and electric elemental to weapons an parry, that's good. The Ancient Blade can one-shot any enemy, including most boss-tier monsters, but breaks after a single use. Light Dragon parts fused will heal you each time you use the item, plus do extra holy damage. It's a narrow mechanic to fuse any two items but very deep as spreadsheets with a hundred thousand combinations. Creative players can create amazing airships with auto-targeting missile launchers raining death from above using only a few simple mechanics.
Another example is alchemy in Nethack. Dip anything into a potion, or mix potions with other potions. Simple A+B mechanic, narrow, but deep gameplay. Simple is making a stack of water potions and dipping with holy water or unholy water, the entire stack becomes holy or unholy water. Healing + speed = extra healing, extra healing + gain energy = potion of full healing. full healing + gain energy = gain ability, booze + potion of enlightenment = potion of sickness, levitation + enlightenment can give gain level, or random. Dip in oil to waterproof or rustproof certain things, a potion of acid can corrode some thing, can dissolve iron bars blocking the way, can remove grease, and so on.
Portal is a great example. In Portal 1 you have a single mechanic - make a hole between two places. They explore a bunch of uses, a narrow mechanic but very deep in exploration. In Portal 2 you have the portal gun plus 3 types of gel. Splash repulsion gel on a turret at it bounces around. Gel bombs can reach unexpected areas, fling and double-fling to launch places, conversion gel to reach exploitable places. Very narrow and easy to understand, yet at the same time very deep when combined with the rest of the environment.
As a series, LoZ has always made particularly good use of “narrow but deep” design, and they look to be doing it again with Echoes of Wisdom.
Other games go wide. Magic the Gathering in particular goes quite wide with about 300 mechanics overall. They do a good job of balance within each set, and mechanics gradually drift to extended sets, then legacy, and a small number were restricted or banned in sanctioned play due to unexpected combinations. Many of them come in families, for example a bunch of “look at the next few cards” like Scry, Surveil, Explore, Hideaway, Clash, and Fateseal, yet each is a variant. The game is also deep because there seem to be endless ways to combine abilities to a wide variety of effects some are comically explosive, like creating thousands of token creatures, near-infinite buffs, but generally relatively balanced, powerful combinations along with counters to each combination which you might or might not have in hand. The explosive combinations usually are a 3-effect combo, giving an opportunity for opponents to dismantle the combo when they see it coming or to overwhelm the opponent before they can trigger it.