In options menu there's difficulty settings and controls. The controls are: Arrow up - jump Arrows left and right - moving left and right Shift - punch (bullshite) Ctrl key - kick (overpowered shite)
Doping on the left side upgrades speed of regaining posture/health, which is also consumed when jumping and attacking, anabolics on the right side upgrade damage.
I honestly know just 2 games by Naive team, and this one is worst of 'em.
Feel free to take your time: game pays cash for successful attacks, so the more times you let enemy to regain health, the more cash you earn in the end. But watch out: losing a round burns all 'salary' to zero.