There is only  Exit.

Mechanics:

Basically something about the properties of light, physically talking
 reflection (bullet bills)
 lightbulbs (coins)
 photon barragement (cluster shooter)
 lazer shooter (Mario's straight fireballs)
 speed of light removing matter (shattering blocks)
 quantic physic of light = misplacing/duplication of photons (invisibility powerup)
 quantic physic of light = misplacing/duplication of photons (stealth boos)
 refraction of light (visual bugs/cutoffs)
 
Credits:
 JamesD28's Bullet Bill Object Interaction
 Isikoro's Stealth Boos by Extra Bit
 ASM's Straight Fireballs
 DiscoTheBat's Start with ...
 
 wiiqwertyuiop's Invisible Power-Up
 
 MiniMawile303's Cluster Bullet Shooter
 
 Carld923's Sea Ruins
 
 qantuum's Soul Blazer - World of Evil
 
 I8Strudel, Roy, lolcats349's Shatter on.. Pack