Reef Signal Guard
A noisy current is flipping the reef's glow signals! Build a check-bubble program that spots damaged messages before the fish follow them.
🧠 Before we start
At the Oasis Cache, you learned that saved information can become stale. Information can also change while it travels. A parity check adds one helper signal so the receiver can notice a one-signal mistake.
Arrange the guard recipe
Tap four visual instruction blocks in the order a safe signal program uses them.
Build three safe packets
Count the glowing data pearls. Choose the helper pearl that makes the whole packet's ON total even.
Catch the flipped signal
Compare what left the lab with what reached the reef. The receiver sees an odd total. Should it trust the packet or ask for another?
Debug the stale helper
The sender changed one data pearl but reused the old helper. Repair the program before this packet swims away.
🌟 What you learned
- A packet carries message data and extra check information together.
- Even parity chooses a helper bit so the total number of ON signals is even.
- An odd total at the receiver warns that one signal may have flipped.
- A failed check should trigger a retry, not a guess.
- When data changes, its check information must be recalculated.