You cannot just drag the boxes into the boat, you need to “launch” them. There are constrains for the mouse and when you get too close to the right or to the top of the screen, it automatically drops the box, keeping the momentum of the mouse dragging.
The art was made in three ways: photographies, image composition and 3D rendering. All of the images are processed in PixelOver with a indexed palette, and many have a glitch shader over them made in Godot directly.