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Science/Culture Overflow Bug Fix

For the sake of simplicity I only describe Science here, the same is true for Culture.

Suppose that your science yield is 30 Science per turn, and you're now researching Pottery, which cost 25 Science. On the next turn, Pottery is completed, and you will get 5 Overflow Science. If now you chose to a research Writing, which cost 50 Science, then on the third turn your research progress will be 35/50.
Now consider the case that you switch to Mining (which also cost 25 Science) rather than Writing. Then on the third turn you will have 10 Overflow Science, with 5 comes from the first turn and 5 comes from the second.

There are some bugs (or, features) about Overflow Science:

• You may only research one technology in a single turn. Suppose that your Science yield exceeds the Science cost of technologies a lot. Though excess Science is kept as Overflow Science, but you can only accumulate it each turn, but never make use of it, even if the overflow itself is enough to complete a single technology. This becomes a real problem on later period of game when trying to get a quick Science Victory.
  
• Thought completing a new technology, using turn-based science yield, will accumulate Overflow Science, but using abilities that grant one-time science within a turn (for example, Great Scientist Margaret Mead, which gives 1,000 Science when activated) will not. Suppose that you now have 1,000,000 Overflow Science, and activate Margaret Mead on a 100-cost technology. Then the technology is completed, but your 1,000,000 Overflow Science will be lost and replaced by 900 Overflow Science from Margaret Mead.
  
• Also, using abilities that grant one-time science will not make use of Overflow Science. Suppose in the above case you active Margaret Mead on a 2,000-cost technology. Then you'll get research progress 1,000/2,000, and your 1,000,000 Overflow Science stays where it is.

I added a virtual technology called the Overflow Technology. It is placed after Future Technology, so you can never research it normally, but you can click the Science yield label on the top left corner to research it.
Your research contributed to this Technology can be transferred to any other Technology you're currently researching, also by clicking the Science yield label. Any excess Science is still stored in Overflow Technology.
So the basic procedure to use this mod is as follows:

• Click Science yield label to switch to Overflow Technology.
  
• Contribute Science to that Technology, for example end your turn or activate Margaret Mead.
  
• The overflow text will appear on the Science yield label.
  
• Switch back to the Science you want to research, then click the Science yield label again. You may repeat this until all Science in Overflow Technology is transferred to normal Technologies.

• Research multiple Technologies in a single turn. By contributing your turn-bases science to Overflow Technology, you can manually distribute them on the next turn, completing any number of Technologies as long as your have enough Science.
  
• Fix bugs about one-time Science. Using the above technique, you can ensure that no Overflow Science is left by contributing them to Overflow Technology and then transfers to normal technologies. Then you're safe to active your one-time science ability. You can also put these science into Overflow Technology so you can distribute them into multiple smaller technologies.
  
• You can complete a Technology on the same turn as you trigger its Eureka, without wasting any Science. To do this, research that Technology until you can complete it in 1 turn with Eureka. Switch to Overflow Technology on some turn before triggering Eureka, then use Science in Overflow Technology to complete it on the same turn as triggering Eureka.

• You cannot stack all your Science in Overflow Technology, and make the decision about what to research later. This mod only allow you to stack 1 turn of Science, since at start of turn your current research will be automatically switched to a normal technology if you are now on Overflow Technology; and you can only switch to Overflow Technology if no Science is stack there.
  
• This mod does not interact with the original Overflow Science mechanism: it will not automatically transfer your Overflow Science into Overflow Technology (since the Overflow Science is an inner value and cannot be seen or edited by mods). This mods only provides a way to save your excess Science without touching the original Overflow Science mechanism: for example, you can switch to Overflow Technology every time you're about to complete a Technology, then use Science in Overflow Technology to complete it on the next turn, and transfer excess Science to the next Technology you're researching. But this requires manual operation, so I recommend to use Overflow Science mechanism as usual in early game, and use this mod only when you need it. When doing this, remember first distribute your Overflow Science by researching Overflow Technology on some turn before using any other functions of this mod, or there is still a chance that your Overflow Science gets lost.
  
• Be aware of Galileo Galilei and similar effects. Rather than calculating the total one-time Science and grant it, Galileo Galilei will grant Science multiple times based on the number of Mountains. So if you try to complete multiple technologies with him, the last Overflow Science will replace all other Overflow produced by himself. Therefore It is highly recommended to put all Science of Galileo Galilei into Overflow Technology and manually distribute it.