Multi Nukes = Red and a "flower" pattern of blues around it. Make the red range see the road and make the blue range NOT see the road.
Poison Gas = RGB with red seeing the road.
Nukes do 5 Billion damage. At about level 170'ish mobs have more than 5B health so the key is to build more poison combos so you literally stop the mobs on screen so you can nuke them multiple times.
Fun game