You have three moves at your disposal throughout this journey: a long-range beam weapon, short-range power shots, and shields that reduce damage, but restrict weapon fire. All three of these moves are upgradeable as you progress along in the game.
The Lite version of this game is completely free and has no restrictions on the core gameplay. There are no advertisements, no in-app purchases, and no limits placed on play time. The Lite version of this game simply does not include audio assets in order to increase download speeds. This also reduces the amount of memory that the game takes up on your device.
For more information and documentation about the game, visit: http://neurocryptonics.com.