Chinese Dice Program for the Sinobit

Here is a die rolling program for the Sino:bit.
The right button rolls 1 die, resulting in a 1-6. The left button rolls 2 dice, resulting in 2-12. I used the Chinese Character Bitmapper app I made to get the bitmaps for the numbers, and put them in an array so they could be called in a loop.
I don't know Chinese so it was interesting to learn the Chinese number system works differently than I am used to. Zero doesn't factor into it and 10 has its own character. Then 11 and 12 use the character for 10 combined with 1 and 2, respectively. So I chose to alternate 10 + 1 and 10 + 2 to represent those numbers. In order to prevent a delay from blocking the button detection while the 10 and 1 or 2 are alternating, I used a simple timer algorithm.
The other thing I learned to do is split a 2-digit int into separate digits, in order to display the 10s or 1s part of 11 and 12. I found out that getting the modulus 10 of the number worked to get the remainder in the ones place (byte digit = num % 10;).

 #include <sinobit.h>  
 Sinobit matrix = Sinobit();  
 static const uint8_t digits[][24] PROGMEM {  
  {  
   // char bitmap of 零 ling 0  
   0xff, 0xe0,  
   0x04, 0x00,  
   0xff, 0xe0,  
   0xb5, 0xa0,  
   0x8e, 0x20,  
   0x31, 0x80,  
   0xdf, 0x60,  
   0x00, 0x00,  
   0xff, 0xe0,  
   0x04, 0x20,  
   0x04, 0xe0,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 一 yi 1  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0xff, 0xe0,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 二 er 2  
   0x00, 0x00,  
   0x7f, 0xc0,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0xff, 0xe0,  
   0x00, 0x00,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 三 san 3  
   0x00, 0x00,  
   0xff, 0xe0,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x7f, 0xc0,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x00, 0x00,  
   0xff, 0xe0,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 四 si 4  
   0xff, 0xe0,  
   0x91, 0x20,  
   0x91, 0x20,  
   0x91, 0x20,  
   0x91, 0x20,  
   0x91, 0x20,  
   0xa1, 0xe0,  
   0xc0, 0x20,  
   0x80, 0x20,  
   0x80, 0x20,  
   0xff, 0xe0,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 五 wu 5  
   0xff, 0xe0,  
   0x08, 0x00,  
   0x08, 0x00,  
   0x08, 0x00,  
   0x7f, 0x80,  
   0x10, 0x80,  
   0x10, 0x80,  
   0x10, 0x80,  
   0x10, 0x80,  
   0x10, 0x80,  
   0xff, 0xe0,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 六 liu 6  
   0x04, 0x00,  
   0x04, 0x00,  
   0xff, 0xe0,  
   0x00, 0x00,  
   0x00, 0x00,  
   0x11, 0x00,  
   0x11, 0x00,  
   0x20, 0x80,  
   0x20, 0x80,  
   0x40, 0x40,  
   0x80, 0x20,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 七 qi 7  
   0x20, 0x00,  
   0x20, 0x00,  
   0x20, 0xe0,  
   0x2f, 0x00,  
   0xf0, 0x00,  
   0x20, 0x00,  
   0x20, 0x00,  
   0x20, 0x00,  
   0x20, 0x20,  
   0x20, 0x20,  
   0x3f, 0xe0,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of  八 ba 8  
   0x11, 0x00,  
   0x11, 0x00,  
   0x11, 0x00,  
   0x11, 0x00,  
   0x11, 0x00,  
   0x20, 0x80,  
   0x20, 0x80,  
   0x20, 0x80,  
   0x40, 0x40,  
   0x40, 0x40,  
   0x80, 0x20,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of 九 jiu 9  
   0x10, 0x00,  
   0x10, 0x00,  
   0xff, 0x00,  
   0x11, 0x00,  
   0x11, 0x00,  
   0x11, 0x00,  
   0x11, 0x20,  
   0x21, 0x20,  
   0x21, 0x20,  
   0x41, 0x20,  
   0x81, 0xe0,  
   0x00, 0x00,  
  },  
  {  
   // char bitmap of  十 shi 10  
   0x04, 0x00,  
   0x04, 0x00,  
   0x04, 0x00,  
   0x04, 0x00,  
   0x04, 0x00,  
   0xff, 0xe0,  
   0x04, 0x00,  
   0x04, 0x00,  
   0x04, 0x00,  
   0x04, 0x00,  
   0x04, 0x00,  
   0x00, 0x00,  
  }  
 };  
 int wait = 500;  
 int num = 0;  
 byte dice = 0;  
 int lastTime = 0;  
 boolean firstDigit = true;  
 void setup() {  
  matrix.begin();  
  pinMode(SINOBIT_BUTTON_A, INPUT);  
  pinMode(SINOBIT_BUTTON_B, INPUT);  
  matrix.clearScreen();  
 // Serial.begin(9600);  
 }  
 void loop() {  
  if (!digitalRead(SINOBIT_BUTTON_A)) {  
   dice = 1;  
   roll(dice);  
  }  
  if (!digitalRead(SINOBIT_BUTTON_B)) {  
   dice = 2;  
   roll(dice);  
  }  
  displayNum();  
 }  
 void roll(byte numDice) {  
  byte maxRoll = 0, minRoll = 0;  
  switch (numDice) {  
   case 1:  
    minRoll = 1;  
    maxRoll = 7;  
    break;  
   case 2:  
    minRoll = 2;  
    maxRoll = 11;  
    break;  
  }  
  float rollTime = 1;  
  float rollTimeChg = .1;  
  for (int i = 0; i < 60; i++) {  
   num = int(random(minRoll, maxRoll));  
   matrix.clearScreen();  
   displayNum();  
   delay(rollTime);  
   rollTimeChg *= 1.1;  
   rollTime += rollTimeChg;  
  }  
  switch (numDice) {  
   case 1:  
    minRoll = 1;  
    maxRoll = 7;  
    break;  
   case 2:  
    minRoll = 2;  
    maxRoll = 13;  
    break;  
  }  
  num = int(random(minRoll, maxRoll));  
  matrix.clearScreen();  
  displayNum();  
 // Serial.println(num);  
 }  
 void displayNum() {  
  if (num < 1) {  
   matrix.clearScreen();  
  } else if (num < 11) {  
   matrix.drawBitmap(0, 0, digits[num], 12, 12, 1);  
   matrix.writeScreen();  
  } else {  
   if (lastTime + wait < millis()) {  
    lastTime = millis();  
    firstDigit = !firstDigit;  
    matrix.clearScreen();  
   }  
   byte digit = num % 10;  
   if (firstDigit) {  
    matrix.drawBitmap(0, 0, digits[10], 12, 12, 1);  
   } else {  
    matrix.drawBitmap(0, 0, digits[digit], 12, 12, 1);  
   }  
   matrix.writeScreen();  
  }  
 }  

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