Replace concrete shed floor

I have a 2.5 x 4.75m brick built shed building at the end of the garden. Boards and laminate flooring were laid a few years ago, but the wood became rotten and laminates buckled. These have been removed. Underneath is concrete that covers most of the floor space though uneven. What are my options? I just want to use the room to store garden stuff, kids bikes, gym kit etc.