John Deere L120 won’t start, no headlights

My John Deer L120 won’t start. Lights will not come on. Battery voltage measures 12V. I cleaned the battery terminals. Still won’t start. I discovered the fuse near the solenoid was bad so I replaced the 20A fuse. Tried to start. Heard some clicking (solenoid I guess?) and saw sparks coming from negative terminal. Then nothing after that. I replace the selenoid. Still won’t start and still no headlights. This seems to be an electrical issue of some sort. It should not be spark plugs as I don’t think it even gets that far.

Turn on the headlights, wiggle the battery cables at the terminals. Not unusual for the cable end to get corroded in the terminal. The sparks were telling you something, maybe?

And the spark plugs do not work off the battery.
If battery voltage gets to the coils it destroys them.