Since I'm playing a lot on my notebook I'm sometimes forced (by various circumstances) to play on the touchpad.
While it is definitely possible and not as a pain as it might seem, it is a bit harder than using the mouse.
I found out that with some practice I was able to play against Hard AI quite well (won most of the time) and even the campaign is playable (most missions on Medium though, many Hard achievements are much harder to get when using the touchpad).
The key to success is to use the keyboard as much as possible.
Everything should be mapped to a group - units, workers, production buildings.
Use space to get to the action immediately when something happens.
With some training, you should be ok.
I wouldn't however attempt to play against people in 1v1 Quickmatch, especially if you are ranked gold or higher.
gaming.stackexchange.com/users/1297/PeterK
Obviously, it can be argued on, but I've yet to see someone playing on a touchpad with the same speed and accuracy he has on a mouse.
And considering the fact that Starcraft II is not the most slug-paced game around, it'll probably leave you a bit frustrated.
You could try getting used to a trackball, though. :)
gaming.stackexchange.com/users/1720/idan315
I'm going to say no.
You can play single player, but once you hit the ladder and multiplayer, the mouse control, speed and accuracy will greatly affect what you can do and how you can compete at certain levels.
Short answer:
Your micro will be weak and your macro could technically take a hit as well.
Advantage: Playing with a touchpad could potentially help with your hotkeys and you will be in a good position when you do get a mouse.
gaming.stackexchange.com/users/2084/Latency
I played it for a while using the Apple Magic Trackpad.
It was playable, but I did find that i was at a disadvantage in fast paced games.
Playing against the AI wasn't so bad though.
I think if Blizzard implemented some support for multi-touch gestures, it would make it much easier.
gaming.stackexchange.com/users/303/Jasarien
While it might be enjoyable, I sometimes play without a mouse on my laptop to force myself to use the keyboard more.
It's more of a practice exercise, as one of my weaknesses is macro-ing up my army while attacking.
It's really ineffective to mouse back to your base to produce units and then back to the attack.
Playing on the touchpad has made me a better keyboard user, which has improved my enjoyment when I actually do use a mouse.
gaming.stackexchange.com/users/2720/lecrank
Just switched to a mouse today, as I've been playing on a Macbook for the past couple of weeks.
I'm brand new to StarCraft
so I'd suck either way, but I do notice that because right clicking with the Macbook requires the command key, it's incredibly difficult to use hotkeys with the trackpad.
I probably won't ever go back, my APM increased by 20 just because I was able to use the hotkeys more efficiently with the mouse.
gaming.stackexchange.com/users/None/
I have a mouse, a touchpad and a trackball, and I always use a combination of the trackball (if I need really accurate movement when microing something) and the touchpad (when I'm using the keyboard almost exclusively - when I'm macroing hard).
I just find it easier to play with a trackball than a mouse generally, and using the touchpad allows me to comfortably use all of the hotkeys at once.
gaming.stackexchange.com/users/41153/Blue Sam
Well, I use an MBP without a mouse and I do just fine-
but I haeve yet to attempt with one.
I don't feel frustrated with the trackpad speed or accuracy, but I would love some gesture controls.
gaming.stackexchange.com/users/None/
I would like to play with StarCraft 2 on my MacBook Pro but I often (bad habit) use my laptop sitting on the couch where Mouse is not an option.  Do you think I could be able to fully enjoy StarCraft just using the MBP touchpad?
Can I play and fully enjoy Starcraft 2 using a Touchpad and not a Mouse?
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<starcraft-2>
gaming.stackexchange.com/questions/8246
gaming.stackexchange.com/users/1869/systempuntoout
The touchpad is a disadvantage in fast-paced games in relation to a mouse. While it is a moot point it seems, and it is playable, it is generally agreed upon that you will be at a disadvantage when playing with other people.
Users agree that players without a mouse are at a disadvantage compared to people with a mouse.