This game is a really fresh submission. I had a lot of fun playing this.
Firstly, I really love the menu style. I do think the portal placement desperately needs some labelling. At the beginning I was paying for portals and not placing them. I think what would take this game to the next level would be portals that spawn different types enemies. Creating a need to carefully place your portals in strategic locations. I do respect that this game is designed with casualness in mind and perhaps the added complexity would ruin the feel of the game. That being said I loved the choice to move away from the conventions WASD. It made the game very chill paired with the perfect music for slaughtering blob.
Overall, really great job especially for your first entry. Well done.