Whack-a-Mole (Arduino)

• Starts with 3 lives. Each round lights one of three LEDs at random.
• Hitting the matching switch inside the window scores: red 10, yellow 20, green 30. The payout is tiered, so reaching for the far switch is worth more.
• Missing the window costs a life. At zero lives the LCD shows GAME OVER, and the reset button restarts at score 0 with 3 lives.
• The LCD shows running score and lives on two lines. Each successful hit is also logged over serial at 9600 baud.

LEDs sit behind current-limiting resistors. Switches are read active high, so each needs a pull-down to ground.

Responsive polling instead of a blocking wait. The obvious implementation is delay(2000) and then read the switch once, which registers a hit only at the end of the window and feels broken. Instead the round loops 2000 times with a 1 ms delay(), polling the switch every pass and breaking immediately on a hit, so a press registers within about a millisecond. The remaining window time is discarded on a hit, which is intended.

Parallel constant arrays. LEDS[3] and BUTTON_STATE[3] are indexed by the same random number, so one random(0, 3) picks both the LED to light and the switch to watch. That is what keeps the round logic to a single branch instead of three.

Difficulty ramp. The window starts at 2000 ms. Crossing a score threshold (every 150 points) sets the window to LED_ON_TIME_MSEC / 2, i.e. 1000 ms.

LCD formatting. sprintf into a fixed 16-char buffer with trailing spaces ("Score: %d ") so that a score dropping in digit count does not leave stale characters on the display.

See Engineering details above.