Hi Reverie Requiem, thank you for the detailed feedback!
To grow a cell, keep giving it water without reaching the overconsumption threshold, then balance it with nutrients. By alternating between water and nutrients while avoiding excess, the cell will gradually grow until it can divide. The goal isn’t to maintain a perfectly fixed balance, but to move back and forth between the two resources.
The Water Flow upgrade affects how quickly water is added while you hold down the button. Before unlocking it, you need to click once for each dose of water. After unlocking it, you can hold the button down, and each upgrade increases the flow rate.
As cells grow, they require more water, so the upgrade’s effect may become less noticeable, especially while frequently alternating between water and nutrients. Sorry these mechanics weren’t explained clearly enough in the game. Your feedback is very helpful and shows us where the guidance and visual feedback need improvement. Thank you!