Simon game with ATtiny13

The box for Simon game is designed to be laser cut from 3.2 mm thick plywood.

• Red line marks laser cuts.
• Green areas should be engraved to the depth of approx. 0.5 mm.
• Cyan areas should be engraved to the depth of approx. 1.4 mm.
• Blue areas should be engraved to the depth of 2.3 mm (M3 nut height).

Bottom wall is removable and fixed by four M3 × 16 mm countersink screws.

The M3 nuts are set in the top wall which is glued to four side walls.

Four small L-shaped parts should be glued to the inner corners of the box (to reinforce the plywood under the nuts).

Small cross-shaped parts should be glued to the bottom wall under four button switches.

Files for laser cutter are in the download section.

In a discussion below the project review [RÖB] asked if a linear congruential generator is better that a linear feedback shift register or how are they different.

So I have tried an example for the 16-bit maximal-period Galois LFSR from Wikipedia. The result is really not bad as you can see in the pictured data (only a subtle vertical pattern can be noticed):

The Wikipedia example was slightly modified to work with seed = 0 (period of this LFSR is only 65535):

uint8_t simple_random4() { // using LFSR instead of LCG
  for (uint8_t i = 0; i < 2; i++) { // we need two random bits
    uint8_t lsb = ctx & 1; // Get LSB (i.e., the output bit)
    ctx >>= 1; // Shift register
    if (lsb || !ctx) { // output bit is 1 or ctx = 0
      ctx ^= 0xB400; // apply toggle mask
    }
  }
  return ctx & 0b00000011; // remainder after division by 4
}

Because ATtiny13 can't use MUL instruction but linear congruential generator uses a multiplication, the linear-feedback shift register is more effective and uses 22 bytes less space in flash memory (modified source and HEX file are in the download section). So maybe I can add some additional feature in the future.

The project of Simon game was developed as an electronic set for ÚDiF alias Amazing Theatre of Physics.
The aim was to create a simple toy to teach basic skills in electronics.

The first version (summer 2015) was driven by ATtiny45 or ATtiny85 microcontroller, which has 4 or 8 times more flash memory than ATtiny13. It used many not-so-much effective Arduino libraries.

During winter 2015/2016 I developed a simplified version to fit into a cheaper microcontroller. But it wasn't able to store best score into EEPROM.

In autumn 2016 I decided to rewrite and optimize the program and squeeze almost all functions into 1 kB of ATtiny13 microcontroller. I made some improvements in pseudo-random generator and made minor changes in combo-keys (for re-starting best-scored game and deleting memory). I also added a demo function (infinite pseudo-random loop).