Okay so I seem to be the only one having merging issues lol, which prevents me for going to bigger waves, but fun game nonetheless
3 years ago(+1)
Thank you very much for playing ! Did you try to drag & drop 2 of the same plants over the 3rd one? This is a little snippet that might help you: 
If it does not work like this, let us know and we will start bug hunting! :D They hurt our plants, lol
3 years ago(+1)
Yeah my bad, found out after a while that you had to drag two plants to make it happen! So no bug here haha, congrats for your game!
3 years ago(+1)
Awesome! Glad to know you enjoyed playing the game! We plan to improve the tutorial and merging mechanics in the future! :D