How to make a automatic boss arena

[NotAMartian]

So suppose you want to fight a boss like Eye Of Cthulhu or other bosses that can be fought in any biome. To start get some Minecart rails by using Wood and Iron bars. Place them higher then the tree's. Making them go up and down is very useful. It can be shown how I made them and a very useful way to do it in this photo depending on tree height and terrain.

Once you make the start it hammer it the first one until it looks like this;

once it does you will be ready to start the main track. follow the instructions above to fully understand how to build it in a way so you can dodge most attacks only using your ranged weapon. Using melee will not be very effective using this tutorial but can be edited to work well. Once you create the main track hammer it to look like the first track did. Place fire places

to give the Cozy Fire buff. Campfires do the exact same. Heart lanterns also work well but are harder to craft.
Summon your boss, And FIGHT! Good luck! and congrats on following my FIRST tutorial! oh wait the player left after the last part. Oh well.

Hope you beat your boss that you wanted to fight! I just found this out today and decided to share it with you guys!