Same mechanics as @snailclaw45 put in the original game. You gain elixer each turn. Use it wisely to attack or grow... or both! You can see how much health you have by hovering over the character.
This is just a re-skin I thought would be cool. Clash-themed Tree Royale. Btw, the color settings are reversed from the original, so green means the button is selected and active. (Yeah I added Clash Royale sounds now :))