ender dragon upgrade

make the ender dragon immune to explosions to stop the speedrun strat and require more skill to win. also add a new phase where the end crystals don't work and the dragon walks on the ground, swiping at you. this would go until the ender dragon is at a quarter health, after which the end crystals activate and it acts like normal. also, once at half health the ender dragon gains and attack that lets it turn into an invulnerable eye of ender which moves around it bursts from charging at the player, this gives the impression the ender dragon is teleporting. (note, this would probuly be the whole game drop)