First of all thanks a lot for playing and for the great feedback.
About the connection, you are right... I should make the game full offline by default and let the player choose. Since its only used for leaderboards anonimous connections, I could just trigger it when the player actually submits a score.
About the difficulty, im still working on it... but yeah, the forest level is way too agresive right now. Not sure if its the enemy density or how they are distributed, I need to keep working on that. You might be right about adding an intermediate level.
You found quite a few bugs... thanks for reporting them, they are already on a list to be fixed.
btw im working on a linux build, not sure when it will be ready but hopefully soon.
Thanks for playing.