var x1=Math.floor(Math.random()*5)+1;
var x2=x1+1;
var x3=x1+2;
var guess;
var hits=0;
var guesses=0;
var isSunk=false;
var y1=Math.floor(Math.random()*7)+1;
var sea=[
		 [],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
		 [null, 0, 0, 0, 0, 0, 0, 0],
];

sea[y1][x1]=1;
sea[y1][x2]=1;
sea[y1][x3]=1;

while (isSunk == false) {
    guess = prompt("Ready, aim, fire! (enter two numbers 1-7):");
	
    if (guess === null) {
        break; 
    }
	
	guess = Number(guess);
	
    if (guess < 1 || guess > 7) {
        alert("Please enter a valid cell number!");
    } else {
        ++guesses;
    }
}


console.log(sea[1]);
console.log(sea[2]);
console.log(sea[3]);
console.log(sea[4]);
console.log(sea[5]);
console.log(sea[6]);
console.log(sea[7]);
console.log(x1,x2,x3);
console.log(y1);