Cool concept you got here! The game is definitely heading in the right direction, just need a some fine tuning to make it better. Many of the things I want to talk about has already been mention by others but here are some feedback I have, hopefully it'll be helpful:
- Audio: The music fits really well, it's quite engaging and keeps the player progressing! However, the game could use a bit more audio feedback, such as when the character dies, when you switch character, environmental (platform moving, spinning blade, etc) and when you enter the door to next level. Additionally, although the sound effects fits well, I felt the volume can be balanced better, for example, the firing sound and level start sound can be rather loud compare to other sounds.
- Visual: The visuals are really well made, well done! Similarly, I wish there're more visual indicator as to which character is the active atm, perhaps highlighting it? Also it's good to hold the scene a bit when the character dies, which you can use this time to add some effects/animation (screen turn blur/fade out, etc) and it'll act as some sort of visual feedback before jumping to the menu.
- Gameplay: The gameplay is simple, easy to understand yet fun and engaging! I love how each characters has their own unique ability for each different situation. There's definitely lots of potential level design to add to the game. Incase player forgets what the each character's ability are, you could also add somewhere for players to read it mid game, perhaps the pause menu?
Overall, I know there's not much time in a week to do all those things above but I do hope these feedback helps you if you decide to take your project further or in your future projects. Anyways, I enjoy playing the game and it's quite well made! Keep it up! ^_^