Good game!
Here is my feedback:
What do I like the most?
- The animations and the graphics.
- The thing (I don't know its name) that is on the top right corner of the screen, how it shows you the room that you entered and the room that you are inside.
- The mechanics of the game.
What didn't I like the most?
- The game is neither challenging nor fun, at least for me. I can run between rooms without getting killed by the enemies. xD
- It takes a while to start the game after pressing Enter on the main menu.
- Press Enter to pause the game.
Bugs/To fix:
- The player got spawned where the diamond spawned. [1]
- The enemy that moves can go underneath the player. []
- When I enter the diamond room, the thing that displays the rooms that entered or I am in doesn't show that I entered the diamond room.
- The health bar is blurred.
Suggestions:
- Maybe, "Press Enter on your Keyboard...", move it down a bit, change it to a shorter one, for example, "Press Enter or Start", and animate it, for example, make it turns and off.
- Maybe, make the enemies interact with each other.
- Maybe, when the player gets damaged, make it flashing instead of changing it's colour to grey.
- Maybe, the texture of the ground make it different from the ground.
- Maybe, hide the cursor.
- Maybe, when the player dies, make a delay of 1 sec.
- Maybe, make the player can collect the diamond.
- Maybe, freeze the game/ make the enemies, and the player can't move if the player founds/collected the diamond.
- Maybe, make the ability to mute/unmute the audio.
- Maybe, display controls on the main menu or at the start of the game.
- Maybe, add a "You Died" scene.
- Maybe, add credits on the main menu.
- Maybe, move a bit the health bar a bit from the corner.
- Maybe, when I enter the diamond room, change the room colour to green on the thing that shows the room that I entered.
Endnotes:
[1]

I hope this is helpful!