Write your first script

An effect you write yourself, typed into the browser, running as native machine code on the device seconds later. No toolchain, no rebuild, no reflash and no reboot. These are the steps of Write a MoonLive effect with the code.

You need a device with lights or the 3D preview, and a light show already running so there is something to replace.

Add MoonLive under the Layer in Effects. It renders nothing and says no script — set the script name, on purpose. A fresh module compiling a default would light every new one up the same, and you would be editing someone else's code before writing your own.

Four lines

In the script box, type a name ending in .mle: mine.mle. The card opens an editor. Type this:

class MyEffect {
  void tick() {
    fill(0, 0, 40);
  }
}

Click away from the editor, or press Ctrl/Cmd+S. The lights turn dim blue. That is the whole loop: tick() runs once per frame, fill(r, g, b) writes every light, and the numbers are 0 to 255.

Make it move

class MyEffect {
  void tick() {
    fill(beatsin(30, 0, 100), 0, 40);
  }
}

Save. The color now pulses, because beatsin(bpm, low, high) returns a value sweeping between the bounds at the tempo you named. Every effect that breathes is doing some version of this.

Give yourself a knob

A number typed into a script is a decision you have to re-edit. A control is one you can turn while watching:

class MyEffect {
  byte speed = 30;

  void defineControls() {
    addControl("speed", speed, 1, 120);
  }

  void tick() {
    fill(beatsin(speed, 0, 100), 0, 40);
  }
}

Save, and a speed slider appears on the card. Drag it: the pulse follows. The slider is a real control, the same kind a compiled effect declares. It persists across a reboot and it is reachable over the API, because nothing about it is special-cased for scripts.

Paint per light

fill writes every light the same. To make a pattern, write them one at a time:

class MyEffect {
  byte speed = 30;

  void defineControls() {
    addControl("speed", speed, 1, 120);
  }

  void tick() {
    int n = width * height * depth;
    for (int i = 0; i < n; i = i + 1) {
      setRGB(i, i * 4 + beatsin(speed, 0, 255), 80, 120);
    }
  }
}

Save. Color now varies along the strand and drifts over time. setRGB(index, r, g, b) is the per-light write, width * height * depth is how many lights the layout placed, and the for is ordinary. A value past 255 wraps, which is what makes i * 4 sweep through hues rather than saturating.

When the compile fails

Break it on purpose: delete a closing brace and save. The lights go dark, the card shows the parse error, and the device keeps running. A bad script costs you a message, not a reboot, which is the point of editing code on a device that might be mounted three meters up a wall. Fix the brace, save, and it comes back.

What you have

A working effect, written in a browser and running compiled on the device. It survives a reboot, it has a control, and it is a file you can copy to another device. MoonLive is the language: every function, the types, and the shipped library to read. Making beautiful effects is what to write once you can write anything.