Z + Up arrow key doesn't work (Undertale)
This, most likely, is a result of your keyboard, not the game. Some keyboards have ghosting issues, especially low end ones. Try to test if Z+UP works anywhere else, such as this website.
This, most likely, is a result of your keyboard, not the game. Some keyboards have ghosting issues, especially low end ones. Try to test if Z+UP works anywhere else, such as this website.