Jinx is the final boss of the game and the overall boss for Spookington. He isn't very hard and attacks in a pattern that is fairly easy to learn.
First, Jinx will create pink shockwaves that will expand like giant rings. Simply jump inside them as they expand to avoid them.
Second, Jinx will raise the 9 blocks you're standing on to a random elevation before trying to hit you with laser eye beams. Simply go from left to right on the same 3 blocks and jump over the beams as they come until he stops.
Third, Jinx will summon fire cannons and will shoot them as many other bosses have done. However he will alter the positions of the blocks you stand on while the fireballs are in mid air and will even spin the blocks around. Keep your attention mainly focused on the fireballs and jump into gaps between waves, making sure you have a place to land along the way.
Fourth, Jinx will create a mini-maze in the 9 blocks with a glowing orb at the end. Get to the orb and hit it to knock it into Jinx and damage him. If you are quick, you can jump the moment you see the orb spawn to jump the maze walls and instantly get to the orb.
Fifth, Jinx will summon smaller enemies to attack you, and they will heal you upon being defeated. The first time you see them you will get Yellow Bees and Giant Worms, the 2nd time will be Red Bees and a Golem from the Yeti stages.
Jinx will repeat from the 1st phase from here and your goal will be the same until you've hit Jinx with 3 Orbs, defeating him.