Earned through the story, complete levels 4 to 7
-Upgrade your LIFE, then DAMAGE, then DEMOLITION statistics first.
-SHOTGUN is easily the most powerful weapon due to the enormous size of its spread-shot, but upgrade any SPREAD or SIZE attributes on all weapons first to maximize enemy kills.
-The only useful SECONDARY ITEMS are the ROCKET and the REVIVE. Make sure they are both full when starting a new level.
-Level 5 (Ferry Ride) is a good level to max out XP/pickups. When the grenades blow up they release upgrade items and it's a level where you can easily gain 100,000 XP.
-XP is earned by killing enemies. You lose 10% of your current XP every time you die!
-Carbon, Newtonium & Titanium are dropped by enemies. Boss enemies typically drop a large number of these.
Thanks to JohnnyRock84, tastefulmrship For the tips