There are several spells/abilities in Starcraft 2 that can be set to auto-cast. When auto-cast is turned on, whenever that spell should be used, the unit automatically casts the spell.
To turn on or off auto-cast, simply right click the spell in the bottom right hand portion of the screen. If the box in the command card starts glowing, auto-cast is turned on. If it does not glow, then auto-cast is turned off.
So what spells can you do this for, and why is it useful?
- Heal (Medivac)
- Auto-cast set on by default, this spell is responsible for healing your Bio army whenever the Medivac selected has attack moved. Never should you turn this off; otherwise, you’ll have to manually hit E and left click a unit to heal each time you want your Medivac to heal any units.
- Build Interceptors (Carriers)
- Every time a Carrier pops out, be sure to turn this spell to auto-cast. That way, every time an interceptor dies, your Carriers will attempt to rebuild them automatically.
- Repair (SCVs)
- When you are under attack, be sure to pull a bunch of SCVs off the line to repair your Bunkers. Setting Repair to auto-cast and leaving idle SCVs near the Bunkers will have your SCVs automatically repair the nearest building/Mechanical unit that needs repairs. This can be particularly useful if you need to repair a Mech army or hold your front Bunker line.
- Charge (Zealots)
- Auto-cast set on by default, this spell is responsible for having your Zealots charge every time they can. Never should you turn this off; otherwise, you’ll have to manually target fire to charge a specific unit and nobody has the APM to do that with each Chargelot.
- Attack Structure (Baneling)
- Sometimes, when you’ve won the game and you just want the other person to leave already, you can morph every single Zergling you own into a Baneling and set this spell to auto-cast. Watch as every building your opponent owns gets wrecked. Not very useful for in-game play though.
- Unburrow (Zerg units)
- If you set this to auto-cast, your unit will unburrow as soon as an enemy unit walks near it. This usually ruins the surprise of your burrowed units, though. It is much better to manually unburrow your Roaches once an enemy squadron is completely on top of your army than to have individual Roaches automatically unburrow one at a time and die one at a time. With Banelings, manually explode them while they are burrowed for a landmine effect – do not rely on auto-cast unburrow to do the job for you.