Topic, Game "Path 4 Mouse (old)"

function rayCast(o1,o2) {
//the value we'll return at the end
rt = false;

//some objects and variables to make checking easier
if (!p1) {
//objects
var p1 = new Object();
var p2 = new Object();
var s = new Object();
var p3 = new Object();
//tile width/height
var sq = 20;
}

p1.x = o1._x;
p1.y = o1._y;
p2.x = o2._x;
p2.y = o2._y;

//y = mx + b
//ah, good ol' slope-intercept
m = (p1.y-p2.y)/(p1.x-p2.x);
b = p1.y-p1.x*m;

//units to increase s.x and s.y by
//for checking collisions along the line
xu = (p2.x-p1.x)/Math.abs(p2.x-p1.x);
yu = (p2.y-p1.y)/Math.abs(p2.y-p1.y);

//s.x and s.x will be the points where we check for collision
s.x = int(p1.x/sq);
s.y = int(p1.y/sq);

if (map[s.y][s.x] != 0) rt = true;
else {
p3.x1 = p1.x;
p3.y1 = p1.y;
//travel along the line
for (n=0; Math.abs(s.x*sq-p2.x) >= sq or Math.abs(s.y*sq-p2.y) >= sq; n++) {
//if this gets higher than 100 iterations, stop
if (n > 100) break;

//fancy maths, help to tell if we should
//increase along the x axis or y axis to
//reach the next tilespace
p3.x2 = ((s.y+(yu+1)/2)*sq-b)/m;
p3.y2 = ((s.x+(xu+1)/2)*sq*m + b);

//reaching the next tilespace
if (int(p3.x1/sq) != int(p3.x2/sq)) {
s.x += xu;
p3.x1 += sq*xu;
} else {
s.y += yu;
p3.y1 += sq*yu;
}

//check for map collision
if (map[s.y][s.x] != 0) {
rt = true;
break;
}
}
}
return rt;
}

//we're assuming you have two movieclips named dot1 and dot2

onEnterFrame = function() {
dot2._x = lastX;
dot2._y = lastY;
dot1._x = lastX = _xmouse;
dot1._y = lastY = _ymouse;
trace(rayCast(dot1,dot2));
}