Power-Ups are one-use combat items used to gain a temporary advantage over your opponent. Each power-up item has a specific purpose and level of strength. Listed is a breakdown of common uses for power-ups.
Field Repari Level 1
Field Repairs: Restores health to all of your units. Higher levels restore more health.
Explosive Ammo Level 1
Explosive Ammo: Increases attack damage on Direct Hits and Critical Hits for all your units. Higher levels increase damage by a larger amount. Lasts 4 turns.
Missile Attack Level 1
Missile Attack: Causes direct damage to one enemy unit. Does extra damage to ships. Higher levels cause more damage.
Air Strike Level 1
Air Strike: Causes direct damage to one enemy unit. Does extra damage to land units. Higher levels cause more damage.
Hungker Down Level 1
Hunker Down: Reduces the damage all of your units take from attacks. Higher levels decrease damage by a larger amount. Lasts 4 turns.
Target Jammer Level 1
Target Jammer: Disrupts the accuracy of a single enemy unit, increasing the likelihood that they will get a Glancing Blow when attacking you. Higher levels disrupt accuracy further. Lasts 4 turns.
Evasion Level 1
Evasion: Makes all of your units harder to hit, resulting in an increased chance that your enemies will score Glancing Blows against you. Higher levels further increase the Glancing Blow chance. Lasts 4 turns.
Accuracy Level 1
Accuracy: Increases accuracy for all friendly units, making you more likely to score Critical Hits. Higher levels increase the chance further. Lasts 4 turns.
EMP Level 1
EMP: Prevents a single enemy unit from attacking. Higher levels last longer.
Posion Gas Level 1
Poison Gas: Causes damage to all enemy units each turn. Higher levels cause more damage. Lasts 4 turns.
Tactical Nuke: Does massive damage to all enemy units. Ka-BOOM!
Source: http://support.zynga.com/cp_articleview?gameId=81&Id=kA160000000Gol8CAC&lang=en_US&loc=en_US
