Huh. The dedicated zoom in/out buttons aren't on the options screen (page up/down). Most players stumble upon being able to use the scroll wheel to zoom in/out while in welding mode. Going to update the options menu and add that somewhere in the tutorial
What specific blocks were difficult to see against the black-to-blue gradient?
The destroyer area is meant to have a couple different ways to get across, including block-spam. The "intended" solution is to build an automatic bridge builder, but as long as the player got a bit more comfortable with the building controls somewhere, its a success.