Stamina

Each player has its own stamina. There are three relevant parameters:
- stamina: used up when dashing and replenished slightly. Stamina increases slightly every cycle. As recovery decreases, less stamina is recovered.
- effort: determines how effective dashing is. The basic idea is that if stamina gets low, effort decreases (with a minimum value given by effort-min) and if stamina gets high enough, then effort increases with a maximum of 1.0.
- recovery: controls how much stamina is recovered each cycle. This is similar to effort except that recovery never increases.
The player can dash only with Power lower than the current stamina. The stamina decreases by the Power.