I like the little sound effects as the bulb jumps, and when you pickup the collectables. I was initially confused by how you pick the collectables up - I didn't know that it's only confirmed as collected only after you touch the ground, and I only figured that out in the ghost rooms. Was there a particular reason for this design choice over immediately picking it up on contact?
I liked the usage of platforms and the ghosts being used depending on the light state. I was confused in the room where you had to jump through the platform in order get ahead of an advancing spiked wall, as it wasn't well telegraphed that I could jump though the thinner platforms. A possible improvement would be to make these types of platforms a different colour.
I would have liked to seen more levels that include both the platforms and the ghosts.
The music is rather fitting for the setting and also because of the ghosts - it gives it a haunted castle vibe. I like the sprite artwork - It is very useful that the spikes have a white border to help them stand out, and that the harmful things are the same colour to make it intuitive to the player that they are detrimental.
A straightforward, light-switching platformer.