press W to turn up the difficulty S to turn it down Every 30 seconds you level up After 5 level ups (lv 6) your health will start to recharge slowly then it will go faster at lv 11 and so on At level 11 (21>31>41>...) the box will shrink it gets harder and harder
Credit to StephenTheCoder for making Undertale Physics Credit to TobyFox for making Undertale