Program Grath3;

Uses
    ptcGraph { FPC ONLY! }, Crt;

Var
    gd, gm : integer;

function Random2(min : integer; max : integer) : integer;
begin
    Randomize;
    Random2 := random (max-min+1)+min;
end;

function ScreenX(x : real) : integer;
begin
    ScreenX := Trunc((GetMaxX+1) / 256 * x);
end;

function ScreenY(y : real) : integer;
begin
    ScreenY := Trunc((GetMaxY+1) / 256 * y);
end;

Const
    gtime = 60;
    time = 1;
Var
    ticks, ticks_cur, gticks, gticks_cur : longint;
    i : integer;

Type bubble=record
    x: real;
    y: real;
    sx: real;
    sy: real;
    ftick : real;
end;

Var
    bubbles: array of bubble;

procedure SpawnBubble(x : real; y : real; sx : real; sy : real);
begin
    SetLength(bubbles, Length(bubbles)+1);
    bubbles[Length(bubbles)-1].x := x;
    bubbles[Length(bubbles)-1].y := y;
    bubbles[Length(bubbles)-1].sx := sx;
    bubbles[Length(bubbles)-1].sy := sy;
    bubbles[Length(bubbles)-1].ftick := 0;
end;

procedure TickBubble(id : integer);
begin
    // add accel
    bubbles[id].x := bubbles[id].x + bubbles[id].sx;
    bubbles[id].y := bubbles[id].y + bubbles[id].sy;

    // respawn
    if (bubbles[id].y <= 128) then
    begin
        bubbles[id].y := Random2(200, 220);
        bubbles[id].x := Random2(100, 156);
    end;

    // x floating
    if (bubbles[id].ftick > 0) and (bubbles[id].ftick <= 128) then
        bubbles[id].x := bubbles[id].x + 0.005
    else if (bubbles[id].ftick > 128) and (bubbles[id].ftick <= 256) then
        bubbles[id].x := bubbles[id].x - 0.005
    else if (bubbles[id].ftick > 256) then
        bubbles[id].ftick := 0;

    bubbles[id].ftick := bubbles[id].ftick + 1;
end;

begin
    SetLength(bubbles, 0);
    // defaults
    ticks := 0;
    ticks_cur := 0;
    gticks := 0;
    gticks_cur := 0;

    // init grathical subsystem
    gd := D8bit;
    gm := m800x600;
    InitGraph(gd,gm,'');

    // spawn bubbles
    SpawnBubble(100, 156, 0, -0.02 / 5);
    SpawnBubble(128, 144, 0, -0.02 / 5);

    // loop
    while True do
    begin
        // exit on key press
        if KeyPressed then break;

        if ticks_cur >= ticks then
        begin
            // process bubbles
            if Length(bubbles) <> 0 then
                for i := 0 to Length(bubbles)-1 do
                    TickBubble(i);
            ticks := ticks + time;
        end;
        inc(ticks_cur);

        if gticks_cur >= gticks then
        begin
            ClearDevice;
            SetColor(WHITE);
            // start point
            MoveTo(ScreenX(80+16), ScreenY(225));
            setlinestyle(SolidLn, 0, thickwidth);
            LineRel(ScreenX(64), 0); // floor
            LineRel(ScreenX(10), ScreenY(-128)); // right wall

            // go back
            MoveTo(ScreenX(80+16), ScreenY(225));
            LineRel(ScreenX(-10), ScreenY(-128)); // left wall

            MoveTo(ScreenX(80+16), ScreenY(225));

            // water
            setlinestyle(SolidLn, 0, normwidth);
            SetColor(BLUE);
            MoveRel(ScreenX(-8), ScreenY(-100));
            LineRel(ScreenX(80), 0);

            SetColor(WHITE);
            // draw bubbles
            if Length(bubbles) <> 0 then
                for i := 0 to Length(bubbles)-1 do
                    Circle(ScreenX(bubbles[i].x), ScreenY(bubbles[i].y), 6);

            gticks := gticks + gtime;
        end;

        inc(gticks_cur);
        delay(1);
    end;

    CloseGraph;
end.