Updating from a tank game to a medieval combat game is interpreted as a complete change of game, which is not allowed on Steam

Steam recommends releasing the medieval version as a new game, automatically granting ownership to Tank Kingdoms purchasers.

I plan to follow this method, and approximately in 10 days after the new game is released, the ownership of the two games will be merged.
Tank Kingdoms will be retired in a few days, and the separately provided medieval version will be removed in 10 days.

Players are advised to manually back up their save files before the 10-day period elapses. The save file location is the same as the game's save location.