'+---------------------------------------------+

'|                Sparks! 2.0                  |

'|                    by                      |

'|              Terry Ritchie                |

'|                05/10/24                    |

'|                                            |

'| Updated for Lesson 18 of the QB64 tutorial  |

'|      https://www.qb64tutorial.com          |

'|                                            |

'| Sparks! 1.0 was written back in 2012 when I |

'| was still relatively new to QB64. This new  |

'| version incorporates coding techniques I    |

'| have learned since then.                    |

'|                                            |

'| This version of Sparks! uses an image of a  |

'| spark instead of drawing the sparks using  |

'| multiple PSET statements. Other speed      |

'| enhancements were also implemented.        |

'+---------------------------------------------+



OPTION _EXPLICIT '        declare all variables



TYPE SPARK '              SPARK PROPERTIES

    x AS SINGLE '        x location of spark

    y AS SINGLE '        y location of spark

    xVec AS SINGLE '      x vector of spark

    yVec AS SINGLE '      y vector of spark

    xVel AS SINGLE '      x velocity of spark

    yVel AS SINGLE '      y velocity of spark

    Fade AS SINGLE '      spark brightness

    Fader AS SINGLE '    spark brightness fader

    Alive AS INTEGER '    spark life countdown timer

    Image AS LONG '      spark image

END TYPE



REDIM Spark(0) AS SPARK ' create spark array

DIM x AS INTEGER '        x location of new spark(s)

DIM y AS INTEGER '        y location of new spark(s)

DIM xv AS SINGLE '        x vector to add to spark(s)

DIM yv AS SINGLE '        y vector to add to spark(s)

DIM Hyp AS SINGLE '      length between mouse x,y and spark(s) x,y



'+-------------------------+

'| Begin main demo program |

'+-------------------------+



SCREEN _NEWIMAGE(640, 480, 32) '                        enter graphics screen

_MOUSEHIDE '                                            hide the mouse pointer

DO '                                                    begin main program loop

    _LIMIT 60 '                                          60 frames per second

    CLS '                                                clear screen

    LOCATE 2, 28: PRINT "SPACEBAR TO SHOOT SPARKS" '    display instructions

    LOCATE 4, 27: PRINT "USE MOUSE TO MOVE REPULSER"

    LOCATE 6, 26: PRINT "LEFT MOUSE BUTTON TO REPULSE"

    LOCATE 8, 30: PRINT "ESC TO LEAVE PROGRAM"

    WHILE _MOUSEINPUT: WEND '                            get latest mouse update

    CIRCLE (_MOUSEX, _MOUSEY), 10 '                      draw repulser

    IF _KEYDOWN(32) THEN '                              is spacebar down?

        x = RND * 640 '                                  yes, x location of new spark(s)

        y = RND * 480 '                                  y location of new spark(s)

        IF _MOUSEBUTTON(1) THEN '                        left mouse button down?

            Hyp = _HYPOT(_MOUSEX - x, _MOUSEY - y) '    yes, get distance from mouse to spark(s)

            xv = (x - _MOUSEX) / Hyp '                  create normalized x vector to add

            yv = (y - _MOUSEY) / Hyp '                  create normalized y vector to add

        ELSE '                                          no, left mouse button is not down

            xv = 0 '                                    no x vector will be added

            yv = 0 '                                    no y vector will be added

        END IF

        MakeSpark 50, 60, xv, yv, x, y '                create the spark(s)

    END IF

    UpdateSpark '                                        update any live spark(s)

    _DISPLAY '                                          update the screen with changes

LOOP UNTIL _KEYDOWN(27) '                                leave when ESC key pressed

SYSTEM '                                                return to the operating system



'+-----------------------+

'| End main demo program |

'+-----------------------+



'------------------------------------------------------------------------------------------------------------

SUB UpdateSpark () ' spark maintainer



    '+-------------------------------------------------------------------------------------------------+

    '| Scans the spark array for active sparks and updates their properties. Will also reset the spark |

    '| array when no active sparks are found.                                                          |

    '+-------------------------------------------------------------------------------------------------+



    CONST WHITE~& = _RGBA32(255, 255, 255, 255) ' full opaque white

    SHARED Spark() AS SPARK '                    need access to spark array

    DIM Index AS LONG '                          array index counter

    DIM NoLife AS INTEGER '                      flag to reset array when dead



    IF UBOUND(Spark) = 0 THEN EXIT SUB '                                            leave if array empty

    NoLife = -1 '                                                                    assume array has no life

    DO '                                                                            begin spark update loop

        Index = Index + 1 '                                                          increment index counter

        IF Spark(Index).Alive THEN '                                                is this spark alive?

            NoLife = 0 '                                                            yes, array has life

            _PUTIMAGE (Spark(Index).x - 1, Spark(Index).y - 1), Spark(Index).Image ' draw spark image

            Spark(Index).Alive = Spark(Index).Alive - 1 '                            decrement spark life

            IF Spark(Index).Alive THEN '                                            is spark still alive?

                Spark(Index).Fade = Spark(Index).Fade - Spark(Index).Fader '        yes, update brightness

                Spark(Index).x = Spark(Index).x + Spark(Index).xVec * Spark(Index).xVel ' update x location

                Spark(Index).y = Spark(Index).y + Spark(Index).yVec * Spark(Index).yVel ' update y location

                Spark(Index).xVel = Spark(Index).xVel * .95 '                        update spark x velocity

                Spark(Index).yVel = Spark(Index).yVel * .95 '                        update spark y velocity

                _SETALPHA INT(Spark(Index).Fade), 0 TO WHITE, Spark(Index).Image '  set image brightness

            ELSE '                                                                  no, spark is now dead

                _FREEIMAGE Spark(Index).Image '                                      free image from RAM

            END IF

        END IF

    LOOP UNTIL Index = UBOUND(Spark) '                                              leave at top of array

    IF NoLife THEN REDIM Spark(0) AS SPARK '                                        reset array if no life



END SUB

'------------------------------------------------------------------------------------------------------------

SUB MakeSpark (num AS INTEGER, ttl AS INTEGER, xv AS SINGLE, yv AS SINGLE, x AS INTEGER, y AS INTEGER)



    '+--------------------------------------------------+

    '| Enters sparks into the spark array.              |

    '|                                                  |

    '| num - number of sparks to create                |

    '| ttl - spark time to live                        |

    '| xv  - x vector to be added to spark (0 for none) |

    '| xy  - y vector to be added to spark (0 for none) |

    '| x  - x location of spark(s)                    |

    '| y  - y location of spark(s)                    |

    '+--------------------------------------------------+



    SHARED Spark() AS SPARK ' need access to spark array

    STATIC Image AS LONG '    persistent spark image

    DIM Index AS LONG '      array index counter

    DIM Dest AS LONG '        current destination image



    '+------------------------------------------------------+

    '| Draw spark image the first time subroutine is called |

    '+------------------------------------------------------+



    IF Image > -2 THEN '                            has spark image been created?

        Image = _NEWIMAGE(3, 3, 32) '                no, create spark image canvas  +---+---+---+

        Dest = _DEST '                              get current destination image  | G | W | G |

        _DEST Image '                                draw on spark image canvas      +---+---+---+

        CLS , _RGB32(64, 64, 64) '                  gray corners                    | W |BW | W |

        LINE (1, 0)-(1, 2), _RGB32(128, 128, 128) '  white outer vertical centers    +---+---+---+

        LINE (0, 1)-(2, 1), _RGB32(128, 128, 128) '  white outer horizontal centers  | G | W | G |

        PSET (1, 1), _RGB32(255, 255, 255) '        bright white center            +---+---+---+

        _DEST Dest '                                restore destination image

    END IF



    '+-------------------------------+

    '| Add sparks to the spark array |

    '+-------------------------------+



    Index = UBOUND(Spark) '                          get last index of array

    REDIM _PRESERVE Spark(Index + num) AS SPARK '    add new sparks to top of array

    RANDOMIZE TIMER '                                seed random number generator

    DO '                                            begin spark addition loop

        Index = Index + 1 '                          increment index counter

        Spark(Index).Alive = ttl '                  spark time to live

        Spark(Index).x = x '                        x location of spark

        Spark(Index).y = y '                        y location of spark

        Spark(Index).Fade = 255 '                    initial brightness

        Spark(Index).Fader = 255 / ttl '            brightness fader value

        Spark(Index).xVel = 9 + RND * 6 '            random x velocity

        Spark(Index).yVel = 6 + RND * 6 '            random y velocity

        Spark(Index).xVec = RND - RND + xv '        random x vector plus passed in x vector

        Spark(Index).yVec = RND - RND + yv '        random y vector plus passed in y vector

        Spark(Index).Image = _COPYIMAGE(Image, 32) ' copy the spark image

    LOOP UNTIL Index = UBOUND(Spark) '              leave when top of array reached



END SUB