Press the flag 2x or else there might be a glitch. It also helps with lag. And thats for even if you want to start the game after dying. Use the up arrow to jump. Click to swing your nail. Right and left arrow keys to move. Yes, This is possible, just very difficult. There is no blood when the Serpent dies.
Feel free to remix and change the character, scene, weapon, enemy, whatever you want. Just no recolors and be sure to credit me :) Boss music - Troupmaster Grimm from Hollow Knight.