I've recently been inspired by several posts on this forum in regards to a new fighting system that takes into account fatigue and energy.
I've been working on my chariot racing game off and on for close to a year now trying to add the fundamental element of energy usage to the game to make it fun and enjoyable.
Here are some design models I've encountered:
1) The most basic design model is simply that a player has a finite amount of energy represented by points and that different actions or a degree of an action use up more or less points. The best example I can find of a mechanic that illustrates this model is Terry Goodchild's "The Metric Mile."
While simple to implement this model has some problems with it. The main problem I see is that the player's actions are not in any way impacted by the degree of energy the player has left (except of course when energy comes to the very end). For a simulation that represents activities that may take long periods of time, this may be unrealistic. For example, a horse race is one long race of slowly decelerating.
2) An improved model is create a relationship between the amount of energy left to the actions that can be performed.
In other words, how much energy you have left at any given time influences the moves you can do or the degree which you can do it. A fighter beginning to tire can't swing the sword as hard as the initial stages of the battle, but can still continue on for some time.
An example of this is another Goodchild's game, "Two Furlongs from Home."
A way to implement this is by having energy chips with different colors (green, yellow and red). You have to use the green chips first, then the yellow and finally the red chips. Once you start exclusively using the yellow chips, you tire and your ability to swing your sword as hard has been decreased for the entire match.
From a design standpoint, I think introducing something like this may be a good thing. For one point, I think it can give the loosing player some hope. For example, let's say you have a boxing game and the one player, who is blocking most of the time, is getting pounded by the other player. While the attacking player still has a lot of gas left, he tires a bit and the player can not attack as hard. The defending player who has not lost a lot of energy (but maybe has taken a few scratches and bruises), manages to strike back on equal footing.
In summary, I think it will force players to pace themselves more, helping to create more interesting decisions.
3) I believe I have taken the previous model one step further by not only limiting a player's actions over the long term (as with the green, yellow and red chips) but from the short term as well (within one turn or a couple).
The basic mechanic is that an action costs x points to do, and you only receive an x amount of points per turn which you can accumulate up to a limit. For example, to make a super thrust takes 8 energy and you 10 energy available. You make the thrust and go to 2 energy. You gain 4 energy per turn. As you tire from such a stenuous maneuver it will take you a couple of turns with low cost actions to build up again to make the super thrust.
I think this can also add more interesting decisions and lead to different strategies.
I myself have used a version of the third model that uses two sources of energy (one that provides energy at a given rate which can increase to a certain limit, and another energy source where you can supply any amount to make up the deficit (used for more strenuous maneuvers). This has seemed to work well for racing chariots. I'll have to test it some more, but I think this is a good way to simulate energy usage.
What do you guys think?
I have been tinkering around with a similar energy system although for a spaceship combat game.
In my system the player has a generator that generates a set number of power units each turn. The player can assign these power units to diferent sub systems (shields, weapons, thrusters, etc). Power not assigned to these systems can be stored in batteries (with a limited capacity) and the batteries can be drained of power if the player needs more power for a particular turn (eg has to recharge the shields quickly).
In your system you might have the 3 coloures of tokens recharge at different rates (eg green chips recharge at 4 per turn, 2 green tokens could be used to recharge 1 yellow token and 2 yellow tokens can be used to recharge 1 red token).
Player's cna then choose what token colour to use to pay for an action (eg a 6 token action maigh be payed for by using 4 green + 2 yellow, 4 green + 2 red, or 2 green +2 yellow + 2 red, etc) or maybe some actions will require a mimimum number of a certain colour of token.