Flashlight App Build

Overview

Students build a simple “flashlight” app that turns a light on or off using button presses, using loops and conditionals. This lesson is the programming bridge to real-world meanings of 0 and opposite states (on/off) as quantities with opposite directions/values, connecting to grade-level Number System ideas about positive/negative and interpreting 0.

Learning intentions

• Students will be able to use conditionals to control program output based on button input.
• Students will be able to use loops to continuously check for input.
• Students will be able to explain what the “off” state means (the value/quantity 0) in the context of their app.
• Students will be able to test and debug their flashlight app to meet the on/off success criteria.

Success criteria

• I can press Button A and the flashlight turns on (consistent, observable output).
• I can press Button B and the flashlight turns off (consistent, observable output).
• I can describe how my program’s “off” state corresponds to 0 in the app context.
• I can explain how my loop allows the app to keep responding to presses.

Curriculum links

• The Number System: use positive and negative numbers together to describe opposite values and explain the meaning of 0 in each situation (app “off” as 0).
• The Number System: use ordered pairs and signs to represent opposite locations (as a quick analogy for “opposite states” on a simple coordinate sketch).
• The Number System: interpret inequalities on a number line (quick transition for “if/else” as “greater than”/“less than” logic).

Lesson structure (45 minutes)

1. 0–5 min · Hook & demo

• Teacher shows a quick demo of an on/off flashlight behavior and asks, “What does ‘off’ mean in numbers or quantity—what value is it?”
• Students do a quick think-pair-share: “If on is one quantity, what is off? What is 0 here?”

2. 5–12 min · Mini direct teach (loops + conditionals)

• Teacher models pseudo-code on the board: a loop that repeatedly checks button states, with conditionals that set the display/output state to ON or OFF.
• Students copy the structure into notebooks as a fill-in template: “Repeat forever → if Button A → ON, else if Button B → OFF.”

3. 12–22 min · Guided build (starter code)

• Teacher hands out starter blocks/code and walks through two core parts: (1) the loop, (2) the if/else logic tied to buttons.
• Students implement Button A = ON and Button B = OFF, then run/test immediately after completing each part.

4. 22–30 min · Debugging sprint

• Teacher sets a 6-minute timer and circulates with a quick troubleshooting checklist: “Does the loop run? Does the conditional match the correct button? Is OFF exactly OFF?”
• Students work in pairs to run a test script: press A (confirm ON), press B (confirm OFF), repeat 2–3 times to ensure reliability.

5. 30–38 min · Math connection check (meaning of 0 & opposite)

• Teacher draws a simple “number line” labeled with off/on states and asks students to articulate what “0” represents when the flashlight is off.
• Students write a 2–3 sentence explanation: “In my flashlight app, OFF corresponds to 0 because… ON corresponds to…”

6. 38–44 min · Quick share-out

• Teacher selects 3–4 students/pairs to share how they implemented the loop and what rule changed the output when buttons were pressed.
• Students observe and note one improvement idea to try (one thing another team did well).

7. 44–45 min · Exit ticket

• Teacher collects a short exit ticket with two prompts: (1) “Circle the correct statement: My loop keeps checking input because…” (2) “In my app, OFF equals ____ because…”
• Students submit independently.

Resources

• Microbit-compatible environment (or class coding platform) with block/code starter project
• Button input documentation sheet (no hyperlinks)
• Student notebook pages: loop/conditional template and 0-meaning explanation prompt
• Projector/board for pseudo-code and simple number line sketch
• Pair debugging checklist (loop running, correct button mapping, OFF truly OFF)
• Headphones (optional) for focused build time

Assessment

• During guided build: teacher checks that students can set ON for Button A and OFF for Button B (verbal check + quick scan).
• During debugging sprint: observe partner testing and whether students use the checklist to locate errors.
• Exit ticket: verify conceptual understanding that “off” corresponds to 0 in the app context and that students can describe loop purpose.

Differentiation

• Support: provide sentence starters for the exit ticket (“OFF corresponds to 0 because…”), and a partially completed code template focusing on only the if/else blocks.
• Support for debugging: offer “button mapping” reference cards showing which block corresponds to which button.
• Extension (light, optional if students finish early): ask students to add a second toggle behavior using a single button (e.g., if currently OFF then turn ON; else turn OFF) using conditionals.
• EAL/SEN: allow students to explain the meaning of 0 orally to the teacher or with a simple diagram (OFF = 0, ON = nonzero) before writing.

Extension (optional)

• Strobe effect challenge (if time remains or during next block): students add a short rapid on/off toggle using a loop to create a strobe pattern while a button is held or pressed.