Hi there, thanks for the complement! The interior floor has been polished and sealed. Both these processes darken the concrete up a little. There are many types of sealants, we'd recommend experimenting with a number of them before committing to one. Each reacts differently with every batch of concrete... No two concrete floor will ever look the same! You are seeing grooves in the floor. These are carefully designed expansion joints that are required in concrete to minimize cracking.

Good Luck!