Builder Building the Buildings In Queue

There should be facility to tell the builder About what should he do when current upgrade is finish like giving a contracts in advance. Rules:- 1)The amount of resource will be deducted after the successful upgrade of current building. 2)If the resource is not available for upgrading predefined building then builder jump next queued upgrade and if there is no queued task builder will go and sleep. 3)If there is multiple builder applied for a queued task then builder who finishes first get the contract. If have more suggestion better than me then post and vote for real heroes means builder.