Thanks for the feedback! I'm glad you liked the environment and how everything interacted.
Yeah, the tutorial definitely needs more work. What's intended is for the player to open the book next to the cauldron, go to the Fire Potion tab, then close the book and place the corresponding ingredients into the cauldron (2 Fire Shards and 1 Wind Shard). As you add the ingredients, the cauldron reacts and the floating chalkboard above it updates to show what's inside.
Once you've put the ingredients in, left-click the cauldron to brew the potion. That spawns the portal to Level 1. Then just left-click the portal to start the tower defense section.
Your point about making the tutorial more obvious is valid, and it's something we're planning to improve.
If you get a chance to play through more of the full game, we'd love to hear what else you'd change. It really helps us figure out what needs the most work.