Pac-Man stacking

This project demonstrates a basic in a funny way how I can create a NFT (ERC721) , Token (ERC20) and a Stacking contract thats provide us a reward in tokens if we stake the NFTs.

Only for funny porpouses I added a lore for this exercise .I decided to use a PAC-MAN domain for this exercise because this is a very clear game that's every onw know and I think make sense for this exercise.

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How It Works

So let me explain the main Contracts

PacDos.sol

This is the token ERC20, represents the dot in the game thats pac-man need to eats

Pacman.sol

This is the NFT ERC721, represent the main character in the game

Board.sol

This is the stacking contract, represent the board in the Game.

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History telling

You can stake your NFT in the staking contract to aern Tokens as a reward or in other words you can throw you Pac-man into the board to see how they farm points.

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Todo

• Create and mint NFT ERC721
• Create and mint Token ERC20
• Stake NFT
• Unstake NFT
• Win rewards in token every 60 seconds for staking
• Claim rewards
• See pending rewards
• Liquidate position
• Tests
• Dockerize project
• Improvements SafeMath

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Liquidation process

We want to add a liquidation option por the NFT in the stacking contract , but what kind of logic we can use?

Now we gonna try to explain my custom logic .

First of all we would call a liquidation process when the health factor will be less than LiquidationThreshold . We would retrieve this health factor from our Board.sol contract from the function healthFactor( tokenId ), and if canLiquidate() is true we would call to asGhostEatsTo(uint256 tokenId) that it is the liquidation function.

To calculate the health factor we will assume this :

• On NFT mint we will mock a fixed value on it, it represents the collateral amount in Borrow/Loan terms
• Every 60 seconds we will generate a random new number to simulate a market price movements
• The Liquidation threshold will be 50%

⚠️ IMPORTANT NOTE: The random number is not a real random , is a pseudo random number , if we want a real random we will need to use a out of chain random provider with some oracle . So with this example we can anticipate when the NFT can be liquidated, because you can know the random before it is generated More information about it here With all this premises we can do the math to calculate the health factor like this .

Hf= HealthFactor, Rn= RandomNumber, Cl= collateral, Lt= LiquidationThreshold.

So the maths are like this : Hf= ( Rn / Lt) / Cl

Example:

• User mint a NFT and the value is 150 on mint , the actual simulate (random) a market price is 100 so the Hf= (100/0,5)/150, the Hf is 1,33. So we are safe :)
• 2 min later the new market price is 75, so Hf= (75/0,5)/150 the Hf is 1 we are near to liquidation but not yet :)
• 5 min later the new market price is 50, so Hf= (50/0,5)/150 the Hf is 0,66 now anyone can call to the function to liquidate us because our Hf is under 1 :(

Workflow

1. UserA mint a NFT, random value assigned , Example: 150
2. UserB check the health factor of the UserB NFT, Example Response: 0.9
3. UserB can liquidate the NFT from UserA

⚠️Note: Right now we don't liquidate anything , we only throw a event Liquidated to simulate this liquidation

More information about liquidation process.

More information about health factor