The Broken Beacon

This activity assumes you have:

  • the Frothy CLI installed (frothy doctor passes)
  • the Frothy VS Code extension
  • a preflashed Frothy Machine plugged in and connected

If you have not connected yet, start with First steps .

The board has a set of words called puzzle.* baked into its base image. They are supposed to work together to display a signal pattern on the LED matrix.

They do not work. Each one is broken in a different way.

Your job: figure out what each piece is supposed to do, fix it, and get the full signal working. The tools you need are words, show, info, set, and to.

Stage 1: What Is Here?

Type words at the prompt. Scan the output for names you have not seen before.

You should find eight names starting with puzzle.:

  • puzzle.x
  • puzzle.y
  • puzzle.dot
  • puzzle.frame
  • puzzle.top
  • puzzle.bottom
  • puzzle.scene
  • puzzle.reveal
Hint

Type words and press enter. The output is grouped by origin. Look past the familiar grid.* and matrix.* families.

Stage 2: What Does It Do?

Pick one of the puzzle words and inspect it before calling it.

show @puzzle.dot

Read the definition. Predict what will happen. Then call it:

puzzle.dot:

A pixel should appear at position (5, 3). That is because puzzle.dot reads two values, puzzle.x and puzzle.y, and lights the pixel at that position.

You can also check metadata:

info @puzzle.dot
Hint

show @name prints the reconstructed definition. info @name prints the value class, arity, and origin of a binding. Try both.

Stage 3: Can You Move The Dot?

The dot appeared at (5, 3) because that is where puzzle.x and puzzle.y point. Change them:

puzzle.x
set puzzle.x to 10
puzzle.dot:

The dot should move to (10, 3).

Stage 4: Fix A Broken Function

Call puzzle.frame:. You should see a single pixel at (0, 0). That is not what it is supposed to do.

Inspect it:

show @puzzle.frame

The definition only sets one pixel and does not clear the screen first. It is supposed to draw a border rectangle around the full display.

Fix it by redefining the word:

to puzzle.frame [
  grid.clear:;
  grid.rect: 0, 0, grid.width, grid.height, true;
  grid.show:
]

Call puzzle.frame: again. You should see a 12x8 border rectangle.

Answer
to puzzle.frame [ grid.clear:; grid.rect: 0, 0, grid.width, grid.height, true; grid.show: ]

Stage 5: Fix A Chain Of Three Functions

Call puzzle.scene:. Nothing visible happens.

This is the core puzzle. Three things are broken at once, and you need to fix all three before puzzle.scene: works.

Start by inspecting the chain:

show @puzzle.scene
show @puzzle.top
show @puzzle.bottom

What you will find:

  • puzzle.scene calls puzzle.top: and then puzzle.bottom:, but it does not clear the screen before drawing or show the result after
  • puzzle.top fills the entire screen instead of just the top half
  • puzzle.bottom does nothing at all

The fix is iterative. Start with puzzle.scene so you can see something on the display, then fix the other two:

to puzzle.scene [ grid.clear:; puzzle.top:; puzzle.bottom:; grid.show: ]

Call puzzle.scene:. You should see the full screen filled. That is the broken puzzle.top overshooting. Fix it to fill only the top three rows:

to puzzle.top [ matrix.fillRect: 0, 0, grid.width, 3, true ]

Call puzzle.scene: again. A filled band appears across the top. Now fix puzzle.bottom to fill the bottom three rows:

to puzzle.bottom [ matrix.fillRect: 0, 5, grid.width, 3, true ]

Call puzzle.scene:. You should see two filled bands with a dark gap in the middle.

Answer
to puzzle.scene [ grid.clear:; puzzle.top:; puzzle.bottom:; grid.show: ]
to puzzle.top [ matrix.fillRect: 0, 0, grid.width, 3, true ]
to puzzle.bottom [ matrix.fillRect: 0, 5, grid.width, 3, true ]

Stage 6: Wire It To A Knob

Call puzzle.reveal:. You should see a filled bar 3 pixels wide on the left side of the screen. Twist the left knob and call it again. Same bar.

Inspect it:

show @puzzle.reveal

The width is hardcoded to 3. Make it respond to the left knob instead.

First, find out what the knob returns:

knob.left:

Twist the knob and try again. It returns a value between 0 and 100.

Now redefine puzzle.reveal so the bar width tracks the knob:

to puzzle.reveal [
  grid.clear:;
  grid.rect: 0, 0, (knob.left: * grid.width / 100), grid.height, true;
  grid.show:
]

Call puzzle.reveal:, twist the knob, call it again. The bar should change width.

Answer
to puzzle.reveal [ grid.clear:; grid.rect: 0, 0, (knob.left: * grid.width / 100), grid.height, true; grid.show: ]

Stage 7: Save Your Work

Type save. Your fixes are now stored on the board.

Type restore. Everything should still work. The board reloaded your saved overlay.

Stage 8: Break Something And Recover

Intentionally break one of your fixes:

to puzzle.scene [ grid.clear:; grid.show: ]
puzzle.scene:

The screen goes blank. Your pattern is gone. Now recover:

restore
puzzle.scene:

The two bands are back. The board returned to your last saved state.

If you had never saved, or your save is also broken, there is a harder reset:

dangerous.wipe

That clears your live overlay and saved snapshot. The board returns to its base image. Your fixes are gone, but base-image words like grid.*, matrix.*, and puzzle.* survive. The puzzle words return to their original broken state, so you can start over.

Next: Missions .