Reach level 2 to unlock the daily challenges. Complete those challenges for extra money. Watch advertisement videos or complete the tasks at the offer wall.
Multi-kills
Wait until an enemy soldier appears directly behind another one. Shoot the one in front to hit both of them.
Power-ups
The following power-ups can be used during battles. After reaching certain levels you will be awarded additional power-ups for free.
Piercing Bullets: Causes one hit kills regardless of hit location.
Slo Mo: Slows down time for the remainder of the level.
Spotter: Marks all enemies on the field.
Progression
To proceed to the next region, kill the Bosses in the Black Ops missions. However, you must upgrade your gun first to qualify, which requires money. Earn money by completing Primary missions, followed by Support missions.
Restore energy
You have to spend energy with each game session. Energy replenishes over time. However, you can restore all your energy instantly by advancing the time on your device. Afterwards, set the time back to its correct value.
Scoring
Your score at the end of a level will determine how much money you earn. You will get bonus points for headshots and multi-kills.
Sniping
Before tagging or firing, take note of your surroundings. You will have about thirty seconds before your enemies will be alerted to your presence. Look for potential escape routes that your enemies will use and take them out when they are running to those locations.
Thermal scope
After obtaining the thermal scope for your sniper rifle, use it in bursts and to tag enemies. To tag, hold the crosshairs over an enemy. A "tagging enemy" meter will appear. Keep the enemy in your sights until it is filled. When an enemy is tagged, a symbol will appear over their heads. To do this effectively, activate your thermal scope, then quickly memorize all enemy locations. Turn off the thermal scope before it expires, then tag as many enemies as possible. This tactic is very useful in missions where you are tasked to kill a specific type of enemy, such as Combat Medics.
Upgrades
Do not upgrade your Support mission weapons as often as your sniper rifle. Only upgrade your Support mission weapons to the point where they are qualified for use for a particular level. Your sniper rifle should be upgraded as much as possible. Besides the damage and accuracy upgrades which are required to progress, also upgrade the scope and thermal. The scope increases its zoom range with each upgrade. Thermal upgrades will allow it to last longer.
Various Tips and Tricks
In order to advance to the next region, you have to take out the boss enemies in the Black Ops missions.
Keep in mind that completeinf the primary and support missions is the best way to progress.
Always aim for headshots and multi-kills!
You don't need to account too much for the movement speed of your target. Just line up their noggin in your crosshairs and pull the trigger.
Don't try to use a sniper rifle in a mission that specifically calls for a shotgun.
Complete the daily challenges for extra cash.
If you have enough money to upgrade an item do it.
Use one of these upgrades to step up your game:
The Spotter instantly marks all enemies on the field.
The Slo Mo slows down time for the remainder of the level, making it much easier to land headshots.
The Piercing bullets will make your bullets kill anything they hit in one shot, regardless of hit location.
Money...