Jump and Movement mechanics felt pretty good.
Level design was pretty good and felt challenging the right amount. The spring mechanics and the ladder contributed well to making the gameplay experience diverse and interesting.
Changing the visuals for night time was really clever - it makes the level slightly hard to see, just like being in the dark. On top of that, the ability to find different items at different times adds a good depth to the gameplay experience as it requires the players to observe and visit every part of the level carefully.
Few things that come to mind are-
1. The Titanium collectables were slightly hard to spot since their colour blended in with the background.
2. Check out this mechanic called "coyote time" - it allows the player to jump within a few frames after walking off a platform, helping the player avoid a death.
3. I did not understand what to do with the cursor.
Overall, it's a nice concept and executed quite well. Nice work!