New battery

  I was not supposed to continue this project but I finally did some more tests : I tried to run the mushroom with a brand new CR2032 coin cell and with a LIR 2477.   And I also removed the potentiometers to avoid wasting any mV from my poor coin cells.
  The results are still sluggish with a CR2032, and it is not working with the LIR2477. I was expecting to get better results with the 2477 but maybe it is too old, it was scavenged from a broken bike light.
  According to the datasheets a LIR2477 has 3.6V and 150-180 mAh  which is better than a CR2032 but I don't know how to interpret the other parameters.   I think that what matters is also how fast it can discharge. I compared the intensity with the 3 batteries :

•   3.7V NiMh : 45-50 mA working fine
•   CR2032    :15 mA, the motor is running slowly, then 30 mA, but with the motor running faster, but then the Attiny85 seems to crash
•   LIR2477   : 2-5 mA  the motor is buzzing, but not really working

Sound
  Another appropriate thing to do with a mushroom shaped box would be to play mario theme or the SuperMario sound sample when Mario take a mushroom and grows up.
  So I tried to use the tone library but it didn't work. According to this ticket [https://github.com/arduino/Arduino/issues/3519], it doesn't work on the Attiny85   because the Attiny family only have a single timer.
  Another solution is to use the TrinketTone library which is supposed to work, or this example. As playing SuperMario theme has already been done,   I wanted to try to play an audio sample instead, but the PCM library I found also requires 2 timers (details) and the ATtiny only has one.
  The last option would be to try to play the sound as it is done in the original SuperMario
  It does make an interesting challenge but I will need to study the NES hardware a bit more.

Wallpaper
  To finish on a brighter and more successful note, I made several brick wallpapers png, nothing complicated but it will save you some work if you need this
  kind of background for your projects ;-)