/*
 *	Copyright Paul Campbell 2011 - licensed GPL 3.0
 */
void setup() 
{
    pinMode(6, OUTPUT); 
    pinMode(7, OUTPUT); 
    pinMode(8, OUTPUT); 
    pinMode(9, OUTPUT); 
    pinMode(10, OUTPUT); 
    
    pinMode(17, INPUT); 
    digitalWrite(17, 1); 
    pinMode(18, INPUT); 
    digitalWrite(18, 1); // enable pullups 
}

unsigned char t=4;
unsigned char mask;
unsigned char left;
unsigned char state;

void loop()
{
    unsigned char v = 0;
    int wait;
    
    if (digitalRead(17))	// decode the input pins
      v |= 1;
    if (digitalRead(18))
      v |= 2;

    if (v != t) {		// if they've changed set up initial conditions
      switch (v) {
      case 0:
        state = 0;
        break;
      case 1:
        left = 1;
        state = 1;
        break;
      case 2:
        state = 0;
        break;
      case 3:
        state = 1;
        left = 1;
        mask = 0x1f;
        break;
      }
      t = v;
    }

    switch (v) {		// perform one step
    case 0:  // count
      state++;
      wait = 500;
      break;
      
    case 1:  // cylon
      if (left) {
        if (state == 0x10) {
          left = 0;
          state = 0x8;
        } else {
          state = state<<1;
        }
      } else {
        if (state == 1) {
          left = 1;
          state = 2;
        } else {
          state = state>>1;
        }
      }
      wait = 200;
      break;
      
    case 2:  // flash
      state = ~state;
      wait = 250;
      break;
      
    case 3: // worm
      if (left) {
        if (state&0x10) {
          if (state == 0x10) {
            state = 0x18;
            left = 0;
            mask = 0x1f;
          } else {
            mask = mask << 1;
            state &= mask;
          }
        } else {
          state = (state<<1)|1;
        }
      } else {
        if (state&0x1) {
          if (state == 0x1) {
            state = 0x3;
            left = 1;
            mask = 0x1f;
          } else {
            mask = mask >> 1;
            state &= mask;
          }
        } else {
          state = (state>>1)|0x10;
        }
      }
      wait = 400;
      break;
    }
    v = state;
    digitalWrite(6, v&1?1:0); 	// light the LEDs
    digitalWrite(7, v&2?1:0); 
    digitalWrite(8, v&4?1:0); 
    digitalWrite(9, v&8?1:0); 
    digitalWrite(10, v&16?1:0); 
    delay(wait);
}