Altoids Geiger counter

My "Remixed Geiger counter" board fits almost perfectly, by chance, in the "classic" Altoids box, with room left for the SI-29 GM tube, the 1100mAh LiPo battery and the 0.96" OLED display.

The ATmega328 processor runs at 8MHz with the internal oscillator, a better choice (than the 16MHz of Arduino 2009) for the LiPo voltage of approx 3.7V.  The display I used is compatible with the monochrome 128x64 OLED display from Adafruit.
It is powered at 3V3, requiring a voltage regulator (78L33, TO-92), placed where the the trim-pot (for adjusting LCD contract) was supposed to be (top-right corner of the board).

The sketch uses Adafruit_SSD1306 library, with the wiring to the display as defined below:

#define OLED_DC 8
#define OLED_CS 7
#define OLED_CLK 4
#define OLED_MOSI 3
#define OLED_RESET 5

Note that the same D3-D8 are used for connecting to the LCD 1602 display in the "regular" DIYGeigerKit.

Also note that I did not install the "click" LED nor the buzzer, relying instead on the OLED display to indicate the radiation level.

Since the lid needs to be open anyway in order to see the screen, I thought it does not make sense to drill 2 holes in the box for the USB miniB connector (used for charging the battery) and the on/off switch. (As well, this sounds like a believable excuse for being lazy.)

If I were to improve on it, I would replace the right-angle toggle switch with a straight-up one (easier to operate), then add a button or two for user inputs (configuration parameters, menu navigation etc). The "click" buzzer and the LED could be made "digital", wired to controller's outputs. Adding a Bluetooth module would be also useful (if it works at all from inside the closed box, I need to try it). Ideally, I would also add RTC, GPS and SD card, for logging purposes. And then it would become a smaller and cheaper version of Safecast bGeigieNano :)