App store and rock drill: what they have in common

1. Step 1. App store — uses — Mobile app. A catalogue.
2. Step 2. Mobile app — uses — Smartphone. For a smartphone.
3. Step 3. Smartphone — has part — LED. The camera flash.
4. Step 4. LED — is part of — Street light. LEDs.
5. Step 5. Street light — is part of — Tunnel. Lighting.
6. Step 6. Tunnel — uses — Rock drill. Driving the Mont Cenis tunnel.

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