For anyone wondering, I was messing with the controls and if you want to do the insert coins settings for a more arcade-ish gameplay, press 6 or 8 (works the same) on yr keyboard, (num lock does not work) then press 5 or 7 (works the same too) to select downwards and 6/8 is the enter button, go to coin assignment and assign "coin slot 1/2" how many credits per "coin". 3 is coin slot 1. 4/5/7 is coin slot 2. Pressing 1/2 is to start. Esc is to literally exit the whole game.
Tip: Left clicking is too tiresome for me so I found spamming A and S key works to shoot as well. Have fun playing this nostalgic game guys! :'>