Heavy Fists

Three rounds. One tank of gas.
Spend it on him, or on staying upright.

Your hands are where you put them Right — attack. Tap = jab, hold = power.
Left — defend. Hold = guard, flick = slip.
Finger height picks head or body, both sides.

Head takes his health. Body takes his gas — and shrinks his tank for good. Empty him and his hands drop: a power upstairs puts him down. Three knockdowns in a round ends it, either way round.
Two hands, one line each W / S — guard high / low. Hold = guard, tap = slip.
/ — punch head / body. Tap = jab, hold = power.
I / K work as well, if you would rather keep both hands home.
Use both hands at once — guarding and punching are independent.

Head takes his health. Body takes his gas — and shrinks his tank for good. Empty him and his hands drop: a power upstairs puts him down. Three knockdowns in a round ends it, either way round.

Infinite gas is the control, not a cheat: same opponent, wrong guard line still costs you health, only the budgeting is gone.
Build 22.