Tutorial 8: Make a simple drawing app with Pen

You will make: a drawing surface where the sprite follows the pointer while the mouse is down. This uses G-Warp's Pen extension; enable it from Extensions before building the scripts.

Step 1 — Enable Pen

1. Save a copy of the project.
2. Open Extensions and add Pen, if it is available in the current build.
3. Select the sprite that will act as the pen tip. Put it at the Stage centre and choose a small costume.

Step 2 — Draw while dragging

Use a looping script to follow the mouse, drawing only while the pointer button is down.

when flag clicked
erase all
pen up
forever
  go to x: (mouse x) y: (mouse y)
  if <mouse down?> then
    pen down
  else
    pen up

If your Pen palette calls its clearing block erase all or shows a slightly different label, use exactly what is in your build's Pen category. The pointer-tracking block is from Motion and the mouse-state reporter is from Sensing.

Step 3 — Add colors or thickness

1. Use the available Pen color block before drawing to pick a new color.
2. Use the Pen size block to set a comfortable thickness. Try two or three sizes and compare them.
3. Add a key-press event for a chosen key to clear the screen with the Pen clear block if you want a reset shortcut.

Step 4 — Test and save

1. Press Start and drag the mouse across the Stage. Lines should appear only while the mouse is held down.
2. Release the mouse and move the pointer without drawing. The pen should lift.
3. Try drawing again after clearing. Save, close/reopen a copy, and check whether your saved project behaves the way you expect.

Gotcha: Pen ink may be cleared when the project stops or restarted depending on the implementation. If you need a permanent drawing, you may need to stamp/export the result or use a paint editor. Do not assume pen strokes become costume art automatically.

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