i made it in 1 day you need to first do 1 skill in science research speed and then go all the way to tree grow skill until max, then go to the tree and around this point you will have 170-200 points (cash) buy the handgun and dont worry on the next attacks (you can buy health with 50 points) but you will be able to do it once just keep growing the tree and it wont be a happy ending :D
PS: Is there a good ending?
 "Nuclear Plant"){kind=icon}
 "Relive Your Life"){kind=icon}
 "Fantasy Online"){kind=icon}
 "Reprisal"){kind=icon}
 "Chronicles of Herenvale"){kind=icon}
 "Nuclear Outrun"){kind=icon}