LICE_Line(licebm, xstart, ystart, xend, yend, color, alpha, LICE_BLIT_MODE_COPY, aa);
  if (envselected)
  {
    if (abs(xend-xstart) > abs(yend-ystart))
    {
      ++ystart;
      ++yend;
    }
    else
    {
      ++xstart;
      ++xend;
    }
    LICE_Line(licebm, xstart, ystart, xend, yend, color, alpha, LICE_BLIT_MODE_COPY, aa);
  }

• LICE_BLIT_MODE_COPY: copies input to output -- if alpha is not 1.0, mixes accordingly
• LICE_BLIT_MODE_ADD: sums input and output -- if alpha is not 1.0, output + alpha*input is used, so for subtraction you can use ADD with alpha of -1.0.
• LICE_BLIT_MODE_DODGE: output = output/(1.0-input), more or less
• LICE_BLIT_MODE_MUL: output = output*input
• LICE_BLIT_MODE_OVERLAY and LICE_BLIT_MODE_HSVADJ: ok I need to go get coffee now. fail.