38 lines, 1 of them comments · 324 tokens, written in 1 seconds for $0.0001

 1  let x, y;
 2  
 3  function setup() {
 4    createCanvas(600, 400);
 5    background(220);
 6    x = width / 2;
 7    y = height / 2;
 8  }
 9  
10  function draw() {
11    stroke(0, 0, 0, 150);
12    point(x, y);
13  
14    let r = floor(random(4)); // 0: up, 1: down, 2: left, 3: right
15  
16    if (r === 0) {
17      y = y - 1;
18    } else if (r === 1) {
19      y = y + 1;
20    } else if (r === 2) {
21      x = x - 1;
22    } else {
23      x = x + 1;
24    }
25  
26    if (x < 0) {
27      x = 0;
28    }
29    if (x >= width) {
30      x = width - 1;
31    }
32    if (y < 0) {
33      y = 0;
34    }
35    if (y >= height) {
36      y = height - 1;
37    }
38  }