had same experience, no useful feedback after 6 hrs of work. it had to meet the provided written spec (js/logic) and visual (css/html) requirements and had to pass an internal test suite which i was not given access to.
the response from the recruiter was just "thanks, but the dev team said 'no', that's all the info i have for you"
the response from the recruiter was just "thanks, but the dev team said 'no', that's all the info i have for you"