Viability: The game seems fully functioning and I haven't run into any bugs or dead ends! Really logical where dialogue trees and and send you back to a main menu/interaction. Inventory works well and fully functional. Only trouble I had was finding an ending but I think given more time I would have fun playing until I found one.
Presentation: Visuals are great and add a lot to the theme of the game. I especially like how you changed the illustration when drinking a mystery potion. Good idea to color-code the inventory with the dialogue options related to them, it made it super clear which potions I was buying. Maybe a little more visual hierarchy in the inventory to make it clearer, but that is a small thing.
Theme: Interesting theme here, I like how you tied the inventory system to the theme of the game and shopping for different potions. I think the concept is fun and there were a lot of great interactions with Greensly.
Engagement: I like how you drop the player right into the action, it allows for experimentation within your game systems. It was very engaging to see what potions had effects on my player stats, I would love to see even more of these if you continue with this project. I think the game description of "can you find all 5 endings?" added a lot to my engagement and I wonder if you could incorporate that more into something like a title screen or help menu to make it more obvious, but I don't think it would be a necessary change.