A small platform, painted black with images of kitchen appliances and living room furniture outlined in bright neon, was celebrated Thursday as the future of housing in Boston’s fast-growing Seaport District.

The platform, with a faux wall on one side, was a mock-up of the ultrasmall apartments under construction at the Seaport’s newest residential building, the Boston Wharf Tower on A Street. With units as small as 450 square feet, the apartments fit Mayor Thomas M. Menino’s call for more affordable housing in the district for young professionals who want to live near work and social attractions.