Thank you for the detailed feedback, I really appreciate it!
First of all, one quick question: have you played the latest version (1.1.5), which features a (kinda) "casual mode"?
If not, you should probably give it a try.
However, I'm aware that the game is hard - and partly not by choice but due to the roughness of the code that I've put together.
I'm definitely trying to learn from the (many) mistakes of this first attempt, and I'm currently working on a new game that will (hopefully!) be more enjoyable also for those who are not hardcore gamers.
(I am anything but a hardcore gamer, after all! :D)
Yes, the tree is tough; and the forest is probably the most confusing level.
The problem you encountered when shooting with the rifle is (likely) because walls, and most of solid instances, use two separate invisibile collision objects: one to block the steps and the other one (slightly offset on the y axis) to block bullets and attacks. I'm pretty sure that trees has just one that serves both purposes.
I will check as soon as possibile, and try to correct the issue.
Also yes, pigs and cows get angry (collectively) if you shoot close to one of them.
You get a hint about that from the warden in the first hut.
The invisibile thing in the graveyard could be theoretically avoided, with a lot of luck, but is meant to be dealt with only once you got a certain object I'm not going to spoil (you get some hints about that from a couple npcs): that's why I preferred to not give any indication to the player about its position.
In theory you can run through it, the problem is once you get hit you have only one second of invulnerability; so, by the time the knockback effect is over, you are vulnerable again.
I'm going to double the invulnerability period in the next release (it was already planned), also to prevent frustrating chained deaths.
I will also add an indicator (at least in the casual mode) to make it clear wether the rifle is loaded or not.
Thanks again! :)