This is a fun short game for a 1st project. I liked how you already implemented important platformer features like jump buffering and variable jump height. However, there is a LOT that can be improved in this game:
- The game has rather unintuitive controls. Make sure that players can walk by using the arrow keys or WASD, jump by pressing space or arrow key up and the attack button could be a mouse click.
- The game's background is rather simple. Consider adding more assets and maybe play around with color. I like that it is already a parallax background
- The level design could see major improvements: Make sure to remove dead ends (e.g. by adding collectables) and also build the world around the core gameplay.
- A short damage indicator (e.g. changing the color to red) for the slime would be nice
- Finally: Please add sound and music to your game. Audio makes a game so much more fun to play and can help a lot with giving players feedback for their actions.
Despite these aspects, I still had fun while playing and think that this game is a solid 1st game project. Keep developing :)