If Your new to Maniac Mania and you don't know how to to the phantom ian or get him i will tell you

how to get phantom ian secret boss battle

All you need to do is play maniac mania and get all the achievements but the last one and music and beat all the challenge and buy everything from lefty sonic shop

How to beat Phantom Ian Boss battle

there several ways to beat him

Doors-

Flashlight-

Camera-

Mask-

Reboot-

Doors

If you hear knocking then close the doors til you hear knocking again which meaning that he is gone but actually close both doors if you hear knocking the first time because he in both doors and wait til you hear another knocking that is a different sound which meaning that he is gone

Light

if you see him in the main hallways coming towards you wait til you hear his laugh which meaning he is in his third pose.

held the laugh at him til he goes aways

Cameras

so in your offices when you see a word saying

Find me or search for me

You must go to every camera til you see him

You have to look at him until he goes away

another way

if you see his face at the camera and it just his face and not the rooms

then you must flip your camera down or switch another camera

Mask

if you hear a vent thump sound then that mean he in the vent but if you hear it the 2nd time then put on the mask until he goes away

Reboot

if you hear static noise and you see him in your offices glitching out or [having a seizure] then open your reboot panel and press the reboot button to reboot him after that he will be gone

oh and the poster in the office that change to Phantom Ian

if you do see it and it said find me with him on it that doesn't mean you have to find him on the camera it not what i mean to find him

and also the poster does nothing I think?

But that is all I have to tell you about the Phantom Ian boss battle

Also the video will help