A single skwerl can be pushed left or right as long as there is nothing in front of it. If there is nothing under a skwerl it will fall. A single arrow can be pushed up or down. Unsupported skwerls fall - they kill you if you are underneath. Arrows kill you if they hit you.
Arrows slide over the tops of skwerls.
Sometimes objects are suspended motionless when a level begins. They remain in this state until nearby movement releases them. Balloons are found on some levels. They rise when released and can be burst by arrows or moved singly by the player. They are harmless but can obstruct movement.