Is Monsterra free-to-play?

Excuse me, could you please clarify if Monsterra is indeed a free-to-play game? I'm interested in trying it out, but I want to make sure there are no hidden costs or subscription fees involved. Is it completely free to download, install, and play without any limitations, or are there certain features or in-game items that require real-world currency to access? Your clarification would be greatly appreciated.