Third time’s the charm…

LDR resistance

• Dark ≈ 1 MΩ
• Room light ≈ 10 kΩ
• Bright ≈ 100 Ω

Illustrative values, not fixed specifications. Check your own LDR: more light means less resistance.

So we choke with 10 kΩ.

Replace the direct A0-to-GND wire with a 10 kΩ resistor.

5V → LDR → A0 junction → 10 kΩ → GND

Verify. Upload.

Open the Serial Monitor at 9600 baud.
Cover the LDR, then shine light on it. Watch the reading change.