Horizon Blockchain Games is — as the name implies — a company building games on the blockchain, along with tools to help others do the same. The company announced today that it has raised another $4.5 million, bringing its total raised to a little over $13 million. Horizon’s first game is Skyweaver, a competitive digital trading card game that taps the blockchain to give players more realistic ownership of their virtual cards. Once earned through competition with other players, cards can be s...