for (i = 0; i < numAdjacentPoints; i++) {
    // set some shorthands
    curr_point = adjacentPoints[i];
    // if there is no previous point, we start with 0
    prev_point = ((i === 0) ? {p: {end: 0}} : adjacentPoints[i-1]);
    // initiate a probability object
    curr_point.p = {};
    // set a start value (the start value is the previous point's end value)
    curr_point.p.start = prev_point.p.end;
    // set an end value (the start value + the point's brightness' share of totalBrightness)
    // -> points with higher darkness (255-b) are more have a higher share -> higher probability to get grown on
    curr_point.p.end   = curr_point.p.start + (255 - curr_point.b) / totalBrightness;
    // if the random value is between the current point's p values, it gets grown on
    if (curr_point.p.start < rand < curr_point.p.end) {
        // add the new point to the path array
        path[path.length] = curr_point;
        // set the point's brightness to white -> it won't come into range any more
        curr_point.b = 255;
        console.log("  we've got a winner! new point is at "+curr_point.x+":"+curr_point.y);
        console.log("  "+curr_point.p.start.toFixed(2)+" < "+rand.toFixed(2)+" < "+curr_point.p.end.toFixed(2));
    }
};

we've got a winner! new point is at 300:132 mycelium.php:269
0.56 < 0.53 < 0.67 mycelium.php:270
we've got a winner! new point is at 301:130 mycelium.php:269
0.67 < 0.53 < 0.78 mycelium.php:270
we've got a winner! new point is at 301:131 mycelium.php:269
0.78 < 0.53 < 0.89 mycelium.php:270
we've got a winner! new point is at 301:132 mycelium.php:269
0.89 < 0.53 < 1.00

if (curr_point.p.start < rand  && rand < curr_point.p.end) {

if (curr_point.p.start < rand < curr_point.p.end) {

if ((curr_point.p.start < rand) < curr_point.p.end) {

if (0 < 0.67) {

if (curr_point.p.start < rand < curr_point.p.end)

if (curr_point.p.start < rand  && rand < curr_point.p.end)