When it stops slowly and the sound of the beam gets faster and then stops, the beam would blast so make your own timing to duck the beam. (Something fun to do is to try and hit the beam. If you had a lightning shield you could whack the beam. Tails could do it too by flying up and using its propelling tail to hit the beam. However, as I said, this is only something fun to do, you cannot destroy the beam.)
Every time the laser beam blasts, the area becomes smaller.
Keep letting the laser beam blast until the last point where everything explodes, the yellow beams dissolve and you are free to go.
Now just keep going on until you reach this place while Robotnik drops down.
Robotnik would move towards you slowly. You can avoid getting hit by the spikes by either jumping across Robotnik or backing.
However, if you touch the space in between the spikes, Robotnik would stop, light his little lighter and ...
Blow!
After a while, Robotnik would rise up and down. Hit him then. For Sonic, Robotnik would rise 4 times. For Knuckles, 2 times.
Tips for Knuckles users: Robotnik would move towards you slowly too but blowing his flame while he moves at certain intervals so be very careful. Midi file for all Act 2 bosses unless stated.
