case 0x1b: quit=1; //Press the escape key to exit the program
          break;
          case '-':
          case '`': clear_screen(); //Clear the screen
          break;
          case '~': vga_mode(19); //reset video mode
          break;
          case ' ': pause=1; //hit spacebar to pause program
          break;
          case '|': steppause=1; //hit ' ' to step in steppause
          break;
          case '%': delnum++; //delay the program's main loop, by one or more milliseconds per loop
          break;
          case '5': {if (delnum!=0) {delnummem=delnum; delnum=0;}  //set main loop delay to zero 
                        else { delnum=delnummem; }  }             //or restore the prior delay
          break;
          case 'T':                           //
          case 't': erasetrails=!erasetrails; //Wipe away previous object draws or not
          break;
          case 'A': zthr*=0.99; if(zthr<1.0)zthr=1.0; //approach unit distance from origin 
          break;                                      //with this perception's z-threshold
          case 'a': zthr+=3.0; //step away from the origin, increasing this projection's 
          break;               //z-threshold distance from the center of the simulated space
          case '[': physdisp=(physdisp+1)%3; //onscreen physics display text readout
          break;
          case 'k': kollisions=!kollisions; //enable/disable particle collisions
          break;
          case 'b': starbreak(); //remove a particle to a distance
          break;
          case 'B': starbreak2(); //drop in another particle
          break;
          case 'o': orbitshot(); //introduce additional particle thrown out and round
          break; 
          case 'r': nstars--; if(nstars==0)nstars=1; //reduce particle number
          break;
          case 'c': centerdists(); //Recenter the momentum and position distributions
          break;
          case 'H': savecopy(); //Save a memory snapshot of the matter simulation
          break;
          case 'h': restoresaved(); //Restore saved matter simulation state
          break;
          case '\\': fpsreadout=!fpsreadout; //Onscreen program speed readout, in frames per second 
          break;
          case '=':               //
          case 'I': nstars=20;    //Twenty particles
          case 'i': init_stars(); //Random distribution of velocities and positions, centered
          break;