Responsive Order Summary Component using Margin, Padding, Flexbox

i learnt how to make use of the hover and the active states and also the Flexbox display mode. During the project i had little bit of a problem making the background responsive, i tried making use of the @media query but it still did not work, or maybe i did not make use of it well. Thanks for taking your time to look through this, Your feedback would be very helpful and Encouraging.