Petal is a programming language for creative coding.

flow_field.ptl

compiling petal…

code → canvas

every demo here is editable.

Hit </> source on any sketch to open its code and change it — the canvas recompiles and re-runs as you type. Click the canvas to fling in more balls.

bouncing_balls.ptl

compiling petal…

edit and it runs liveopen in playground →

// Bouncing Balls — click to add more balls.
// Demonstrates state, frame timing, mouse input, and the drawing API.

state balls = []

let sw = float(screen_width())
let sh = float(screen_height())
let delta = dt()

// Seed with a few balls on first frame
if len(balls) == 0 then
    for i in range(0, 12) do
        let f = float(i)
        push(balls, {
            x: 50.0 + f * 60.0,
            y: 80.0 + f * 20.0,
            vx: 80.0 + f * 15.0,
            vy: 40.0 - f * 8.0,
            r: 12.0 + f * 1.5,
            cr: 80 + (i * 23) % 175,
            cg: 120 + (i * 47) % 135,
            cb: 200 - (i * 31) % 150
        })
    end
end

// Add a ball on click
if mouse_pressed(1) then
    let mx = float(mouse_x())
    let my = float(mouse_y())
    push(balls, {
        x: mx, y: my,
        vx: random(-200.0, 200.0),
        vy: random(-200.0, 0.0),
        r: random(8.0, 28.0),
        cr: int(random(80.0, 255.0)),
        cg: int(random(80.0, 255.0)),
        cb: int(random(80.0, 255.0))
    })
end

let gravity = 600.0

// Physics step
let new_balls = []
for b in balls do
    let nvy = b.vy + gravity * delta
    let nx = b.x + b.vx * delta
    let ny = b.y + nvy * delta
    let nvx = b.vx

// Wall collisions
    let final_vx = nvx
    let final_x = nx
    if nx - b.r < 0.0 then
        final_x = b.r
        final_vx = -nvx * 0.85
    end
    if nx + b.r > sw then
        final_x = sw - b.r
        final_vx = -nvx * 0.85
    end

let final_vy = nvy
    let final_y = ny
    if ny + b.r > sh then
        final_y = sh - b.r
        final_vy = -nvy * 0.85
    end
    if ny - b.r < 0.0 then
        final_y = b.r
        final_vy = -nvy * 0.85
    end

push(new_balls, {
        x: final_x, y: final_y,
        vx: final_vx, vy: final_vy,
        r: b.r, cr: b.cr, cg: b.cg, cb: b.cb
    })
end
balls = new_balls

// === Drawing ===
clear(14, 16, 28)

for b in balls do
    // soft outer halo
    draw_circle(int(b.x), int(b.y), int(b.r + 3.0), b.cr / 4, b.cg / 4, b.cb / 4)
    draw_circle(int(b.x), int(b.y), int(b.r), b.cr, b.cg, b.cb)
    draw_circle(int(b.x - b.r * 0.3), int(b.y - b.r * 0.3), int(b.r * 0.35),
                min(255, b.cr + 60), min(255, b.cg + 60), min(255, b.cb + 60))
end

draw_text("Bouncing Balls — click to add", 16, 12, 14, 200, 200, 220)
draw_text("count: " ++ str(len(balls)), 16, 32, 12, 150, 150, 180)

live gallery