Ellastic Billiard

General descriptions for the game:
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* For level 1: Five doors available, the missiles will disappear right after it hit a target, and there is not friction added to the missile
* For level 2: Three doors available, the missiles still disappear right after it hit a target, and there is a friction of coefficient 0.015
* For level 3: Three doors availbale, the missiles will stay in the pool after collision, there's also friction for missiles. Moreover, the concept of power is introduced,
* the power is the total speed you have, if you press 1, it will give the missile 5 percent of the total speed, 2 for 10 percent, 3 for 20 percent. Also, if you have 50
* missiles or more left at this level, you can use left and right keys to control the location of the upper gate. For every ramaining missile, you also get 2 points of power
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* For hidden level: Only one gate, power is set to 80, cannot move the gate. Missiles cannot interact with missiles anymore, so that the user can only user targets to interact with missiles
* In this level, there is no level up condition, which means that this level is just a free challenge level since is it very hard.
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* For level 3 and 4, the game will end when the power is lower than 30 no matter what. If the power is lower than 30, it will lead to the fact that missiles aren't shooting.
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* Instructions to play:
* Basic rules: You have 80 missiles in total, and use those missiles to hit the targets to get them into the holes.
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* Click to shoot in level 1 and 2
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* In level 3, you have 120 of power for starting, and the system will add 2 points for every missile left.
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* In level 3, use 1, 2 or 3 key to shoot; this corresponds to variable fire power. They use different percentage of your power, and that certain percentage of power will become the magnitude of your missile's speed
* Clicking means to press 2 key
* If you have more than 50 missiles left at the beginning of level3, you can also use left or right key to move the upper gate.
* Don't forget that the power will decrease fast(it's exponential).
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* The game will end if the firepower is lower than 30. The game will end at the instant when the power is lower than 30, so please consider wisely!
* This will not wait until the motion is stopped, because this is a strict rule!
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* After you cleared level 3, you can challenge level 4.
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* In level 4, everything is the same as level 3, except that you cannot move the gate, and missiles cannot interact with missiles anymore.
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