I'm a huge fan of Half-life and Portal so i was very excited to try this out and it was quite good, i love the combination of the Portal aesthetic with the Gravity Gun from Half Life 2
That being said, i think you shouldn't have included the arrows pointing to where you need to go and what you need to do, The whole fun of a puzzle game is figuring out the puzzle yourself and when the arrows literally tell me exactly what to do step by step the game becomes less of a fun puzzle game and more of a walking simulator
I think without the arrows this game would have taken me a good 20-30 minutes to complete, but since the arrows tell me exactly what to do i managed to get through the whole thing in like 5 minutes, i thought the puzzles were quite well designed aswell and understandable so i don't really understand why there is arrows in the first place.
Other than that i really like the way you used the theme, i like how you made it so the player has to pick up the cube and use it to click the Play button which i thought was a smart way to teach the player how to use the Gravity Gun before the game even starts.
Only bug/issue i ran into was the doors being a bit small
I would have loved to play through a version of this without the guide arrows but either way thanks for taking the time to make something!