People, please realize the swaying is not random. When a force is exerted downwards on a static object, it will tend to "squeeze" outwards. Imagine pushing your hand down on a piece of clay, it spreads out. So unless every single one of your pieces is dead centre (try a stack of purples), it's going to sway.
simple way to start off. Go for the green grass one, and just put down 4 shooters on the first 2 bends....gg for quite a lot of levels. Throw one normal monkey down to stop escapees
game is extremely easy. For the early levels, do not rush, but let the enemy come to you and just slaughter them for exp till their morale breaks. Put lots of points into the left side options, and later on in game, simply spam tanks and use support fire. Done.