Steampunk refers to a style of vaguely neo-Victorian architecture, early industrial age machines(e.g. steam engines) and motif of "Ancient/Medieval Technology"(clockworks, gears, counter-weights,etc). Various mechanical contraptions, pipes and vessels that draw a picture of immense power confined in flimsy technology.
Science is represented by alchemical tools and 17th-18th century scientific equipment.
The design direction should avoid electricity(use pneumatics) and compact devices(except for personal use) - Steampunk is about big machines, crude technology and manual control. Steampunk and Gothic aesthethic are merged in neo-Victorian genre, that would combine imposing world of industrial machinery(using elements of decay, grit and rust ) and bleak Gothic design that uses more ancient motifs(Medieval/Mythological europe) without retrofuturistic influences. for reference