Very good game, but upgrades feel unbalanced.
The one thing preventing me from giving this game 5 stars is the unbalanced price increases for each ingredient or equipment upgrade. All of a sudden, the game goes from needing coins to needing a bunch of gems. I can only earn up to 15 free gems a day through watching ads, as the game offers me just 5 video ads for gems per day. The gems being asked for will take at least 2 or 3 days to earn through ad watching, and that is for just 1 upgrade! In my experience with Time Management games, using coins for the first upgrade or 2, followed by needing a combination of coins and gems for middle level upgrades keeps things balanced. Then for the highest level upgrade, using a bunch of gems for a gem only upgrade would feel acceptable.
If the upgrade prices get balanced better, this game will earn the 5th star from me.