hello

Transformations:

• size() -> createCanvas()
• function declarations: void/int/... -> function
• Processing color/int literals: #ff1234-> '#ff1234'

Converted p5.js:

//
// hello
//
function setup() {
    createCanvas(400, 400);
}
function draw() {
    background(0);
    fill("#00ff00"); // Processing color literal
    ellipse(200, 200, 100, 100);
}

Original Processing:

//
// hello
//


void setup()
{
    size(400, 400);
}

void draw()
{
    background(0);
    fill(#00ff00); // Processing color literal
    ellipse(200, 200, 100, 100);
}