import cadquery as cq

# Create a plate with 4 rounded corners in the Z-axis.
# 1.  Establishes a workplane that an object can be built on.
# 1a. Uses the X and Y origins to define the workplane, meaning that the
#     positive Z direction is "up", and the negative Z direction is "down".
# 2.  Creates a plain box to base future geometry on with the box() function.
# 3.  Selects all edges that are parallel to the Z axis.
# 4.  Creates fillets on each of the selected edges with the specified radius.
result = cq.Workplane("XY").box(3, 3, 0.5).edges("|Z").fillet(0.125)

# Displays the result of this script
show_object(result)