There are no levels in Minecraft. It's a Sandbox game. Sandbox means no levels but just a infinite world to play in and build, Minecraft also has no guns, you have to get the mod Wich is a Third Party. Also actually play the game without mods and you will see it's not violent: minecraft.net
All video games have levels. Minecraft may very well hide the guns and other weapons in "mods" but the mods are approved by Mojang or they wouldn't be in the game.