Regardless of what enemy your facing,when playing the Protoss these are some aspects of the race you should keep in mind.
Chrono Boosting : Use this ability as often as possible in the game to boost production,economy and upgrade research .
Early in the game use it extensively on probe production to strenghten your economy .
You cannot chrono boost your allies in a team game,but you can use it if you have controll of their buildings.
Warpgates : These are vital in every competitive match.Besides faster production you can use them to warp units anywhere on the map as long as you have a pylon matrix ready .
You should get the warpgate upgrade from the Cybernetics Core as fast as possible using Chrono Boost.
Pylon placement : Pylons should never be placed in random positions and should be used in conjuction with Warpgates for rapid reinforcements and map controll.Proper pylon placements can also help you avoid disabled buildings when they are destroyed and the energy matrix is cut-off .
Unit Usage :
Proper Army Composition : An optimal protoss army will always be a mix of Zealots,Stalkers and Sentries . There should be a sentry for every 3 Zealots and 3 Stalkers in the formation for proper shielding.From here you can add high tier units like Colossi,Immortals,Void Rays etc. depending on the opposing force.
Zealots : They usually make up the majority of early game formations.As they have a fairly large hp pool,use them to take the bulk of damage your enemy throws at you.Block your enemies from reaching more specialized and valuable units in your army .
Stalkers : Early in the game they are the only counter a protoss player has against air units.As they are ranged keep them behind your Zealots .Protect your Zealots with Stalkers against air units and fast kiting units,like Reapers,Hellions Stimmed Marines and Marrauders.
Sentry : The uses of the sentry are many,from ramp controll to army protection with the Guardian shield,or deception using the Hallucination ability.Keep them behing your Zealots and activate the shield whenever your engage a large force.The Force Field ability is also usefull for separating large formations of enemies .
Immortal : These walkers are best used against armoured units and large damage dealing ground units like siege tanks,thors .Their Hardened Shields also makes them ideal to be on the front line when atacking a base with heavy defenses.
Colossi : Ideal when dealing with large groups of enemies like Terran MMM bioballs,or large Zerg organic formations.
High Templars : Like the Colossus they are used for dealing massive AOE more than anything else with Psionic Storms.The Feedback ability is usefull against enemy units with high energy pools,like Batllecruisers.
High Templars should be trained as soon as your first expansion is ready.
Observer : This should be the first unit produced once the Robotics Facility is ready.Being permanently cloaked the observer is invaluable to enemy scouting and detection of stealth units.
Pheonix : These are the best protoss counter to large air formations.The Graviton Beam ability also enables them to take out key enemy units,like siege tanks before your ground units come under fire.
Void Rays : Great unit for base siege,they can atack both air and ground units.They deal massive ammounts of damage the longer they stay focused on a target .Use them to quickly take out key enemy structures or units,like siege tanks,thors.
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