pragma solidity ^0.4.0;

contract Coin {
// The keyword "public" makes those variables
// readable from outside.
address public minter;
mapping (address => uint) public balances;

// Events allow light clients to react on
// changes efficiently.
event Sent(address from, address to, uint amount);

// This is the constructor whose code is
// run only when the contract is created.
function Coin() public {
    minter = msg.sender;
}

function mint(address receiver, uint amount) public {
    if (msg.sender != minter) return;
    balances[receiver] += amount;
}

function send(address receiver, uint amount) public {
    if (balances[msg.sender] < amount) return;
    balances[msg.sender] -= amount;
    balances[receiver] += amount;
    Sent(msg.sender, receiver, amount);
}
}