I am making a game and i need to deduct the right amount of points. This statement I have doesn't work (the playerPower) part.

```
function checkCol(cell, row){
    var color = map[row][cell];
    console.log(color);
    if (color == "g") {
        alert("Green");
        playerPower -= onGrass - passengerBayPower
    } else if (color == "b") {
        alert("Brown");
        playerPower -= onRock - passengerBayPower
    } else if (color == "w") {
        alert("White");
        playerPower -= onIce - passengerBayPower
    }

```

Is there something wrong with the -= and then -?