Back when I started to get burned out playing normal games of SC, I found a thing called Turret Defense! Check out this flash game of TD!!! http://www.handdrawngames.com/DesktopTD/
There are a lot of turret/tower defense games out there. Take a look at this list of the top ten tower defense games. I've played a six of them, and they're pretty fun.
O.O FUN AND ADDICTIVE! too bad u cant wall XD still i did pretty good on my frist try level 47 >< so close... i totally forgot about upgrading towards the end and massed pellets and made this huge maze of pellets XD it worked too ^.^ and then i had to up the pellets around 38 >< their up kinda sux i should mass squirts instead XD o well i'll try again if i get really bored back to reg. sc ^.^
Lol i played onslaught ALL last year in my computer class. i was addicted to it because it reminded me of the Defense maps on SC, like Stacked and Sunken D. highest level i got on onslaught was like... 180 something. it gets hard after awhile. ><
Hmm, theres a guide with all the different combos if you look at the top of the game theres a Tab for it. but Nuke is 1 red, 2 blues, like you said and Poison gas rockets are 1 blue, 1 red, 1 green. Make sure thier not too close together or else theyll turn into a cluster bomb >< Cluster bombs are good, but nuke + poison gas are better