ok I managed to accidently fix it by randomly clicking in the box until the option to full screen finally appeared again in the corner which fixed it. I played the game for a bit and I really like it I hope to see more to the game like maybe a improvement system for characters' stats, or a character customization option for all controlled characters, or a body fat adjustment option to add the fat wherever the player wants as new available fat gets added to the numbers.
The only things I can criticize at the moment is the stomach fat placement for the mc(which just looks weird, like it is being pinched and picked up), and the hit box for mc's attacks which are not always hitting even under the correct circumstances.