Hello again!
Thanks for the answer, now my level is fully playable!
Once again, I'm impressed with the easy-modding capabilities of Coldest.
To satisfy your curiosity, I resolved how to enter in map editing mode. I knew there was some sort of editor thingy by looking in the gui folder ( that editobject.xml and editormain.xml were really suspicious files
). A quick look at the source code made me guess the next step: Running the game with the map level you want to edit as an arg. Ta da!
But to be honest, I've made the level all by myself, except for the trees, they were added later with the editor.
I've got one last question: Can I upload my level (once it's fully finished) to some coldest-related site if somebody wants to give it a try?