Shoot enemies and earn money to upgrade your weapons with the non-linear upgrade system. Enjoy the 6 free worlds that each contain 45 levels over 5 different game modes.
Controls:
Move: WASD or Arrow Keys
Aim: Mouse
Shoot: Left Mouse Button
Special Weapon: Spacebar
Change Weapon: Shift or Q
Pause: Esc or P
Penalties 
Maya Pyramid Solitaire 
Brick Building 
Swipe Art Puzzle 
Swamp Treck 
El Hefe is Coming 
Golden Autumn Mahjong 
Klondike Solitaire 
Mahjong 
The Last Soldier 
Fruit Blaster 
Spooky Mahjong 
Ultimate Spaceship 4 
Famous Paintings 1 
Tripeaks Halloween 
Battle Gear Portal War 2 
Python Squadron 3 
Casper Casino Escape 
Factory Kingdom 
Famous Paintings 3 
Teddy Bear Zombies Machine Gun 
Jungle Crash 
Forest Bubbles 
Xmas Explorer 
Glauron: dragon tales 
Car Mercedes-Benz Vision Tokyo Concept 2015 Puzzle 
Carrot Fantasy 2: Desert 
Escape the Forest 
The Dark Age 5 
Neon Rotate 
Zuma Ball 
Blow Fish