I gave your game a play. I managed to figure out to start a game by smashing all of the buttons listed in the options page. Once in the game I managed to complete the loop for growing stuff. Unfortunately I don't see where the Spreading theme is represented. It is a good effort in the short amount of time provided.
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Thank you for checking the game and providing some feedback. That starting the game is not obvious is indeed a big issue, thank you for highlighting that. Regarding the it's spreading theme. The weeds spread through the flowerbeds. In the first level they do that at a slow pace to not overwhelm the player in the beginning. The amount of weeds and the speed of spread increases at higher levels.