<div id="dot0" style="position: absolute; visibility: hidden; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <div id="dot1" style="position: absolute; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <div id="dot2" style="position: absolute; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <div id="dot3" style="position: absolute; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <div id="dot4" style="position: absolute; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <div id="dot5" style="position: absolute; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <div id="dot6" style="position: absolute; height: 11; width: 11;"> <img src="bullet.gif" height=11 width=11> </div> <script LANGUAGE="JavaScript"> <!-- hide code var nDots = 7; var Xpos = 0; var Ypos = 0; // fixed time step, no relation to real time var DELTAT = .01; // size of one spring in pixels var SEGLEN = 10; // spring constant, stiffness of springs var SPRINGK = 10; // all the physics is bogus, just picked stuff to // make it look okay var MASS = 1; // Positive XGRAVITY pulls right, negative pulls left // Positive YGRAVITY pulls down, negative up var XGRAVITY = 0; var YGRAVITY = 50; // RESISTANCE determines a slowing force proportional to velocity var RESISTANCE = 10; // stopping criterea to prevent endless jittering // doesn't work when sitting on bottom since floor // doesn't push back so acceleration always as big // as gravity var STOPVEL = 0.1; var STOPACC = 0.1; var DOTSIZE = 11; // BOUNCE is percent of velocity retained when // bouncing off a wall var BOUNCE = 0.75; var isNetscape = navigator.appName=="Netscape"; // always on for now, could be played with to // let dots fall to botton, get thrown, etc. var followmouse = true; var dots = new Array(); init(); function init() { var i = 0; for (i = 0; i < nDots; i++) { dots[i] = new dot(i); } if (!isNetscape) { // I only know how to read the locations of the // <LI> items in IE //skip this for now // setInitPositions(dots) } // set their positions for (i = 0; i < nDots; i++) { dots[i].obj.left = dots[i].X; dots[i].obj.top = dots[i].Y; } if (isNetscape) { // start right away since they are positioned // at 0, 0 startanimate(); } else { // let dots sit there for a few seconds // since they're hiding on the real bullets setTimeout("startanimate()", 1000); } } function dot(i) { this.X = Xpos; this.Y = Ypos; this.dx = 0; this.dy = 0; if (isNetscape) { this.obj = eval("document.dot" + i); } else { this.obj = eval("dot" + i + ".style"); } } function startanimate() { setInterval("animate()", 20); } // This is to line up the bullets with actual LI tags on the page // Had to add -DOTSIZE to X and 2*DOTSIZE to Y for IE 5, not sure why // Still doesn't work great function setInitPositions(dots) { // initialize dot positions to be on top // of the bullets in the <ul> var startloc = document.all.tags("LI"); var i = 0; for (i = 0; i < startloc.length && i < (nDots - 1); i++) { dots[i+1].X = startloc[i].offsetLeft startloc[i].offsetParent.offsetLeft - DOTSIZE; dots[i+1].Y = startloc[i].offsetTop + startloc[i].offsetParent.offsetTop + 2*DOTSIZE; } // put 0th dot above 1st (it is hidden) dots[0].X = dots[1].X; dots[0].Y = dots[1].Y - SEGLEN; } // just save mouse position for animate() to use function MoveHandler(e) { Xpos = e.pageX; Ypos = e.pageY; return true; } // just save mouse position for animate() to use function MoveHandlerIE() { Xpos = window.event.x + document.body.scrollLeft; Ypos = window.event.y + document.body.scrollTop; } if (isNetscape) { document.captureEvents(Event.MOUSEMOVE); document.onMouseMove = MoveHandler; } else { document.onmousemove = MoveHandlerIE; } function vec(X, Y) { this.X = X; this.Y = Y; } // adds force in X and Y to spring for dot[i] on dot[j] function springForce(i, j, spring) { var dx = (dots[i].X - dots[j].X); var dy = (dots[i].Y - dots[j].Y); var len = Math.sqrt(dx*dx + dy*dy); if (len > SEGLEN) { var springF = SPRINGK * (len - SEGLEN); spring.X += (dx / len) * springF; spring.Y += (dy / len) * springF; } } function animate() { // dots[0] follows the mouse, // though no dot is drawn there var start = 0; if (followmouse) { dots[0].X = Xpos; dots[0].Y = Ypos; start = 1; } for (i = start ; i < nDots; i++ ) { var spring = new vec(0, 0); if (i > 0) { springForce(i-1, i, spring); } if (i < (nDots - 1)) { springForce(i+1, i, spring); } // air resisitance/friction var resist = new vec(-dots[i].dx * RESISTANCE, -dots[i].dy * RESISTANCE); // compute new accel, including gravity var accel = new vec((spring.X + resist.X)/MASS + XGRAVITY, (spring.Y + resist.Y)/ MASS + YGRAVITY); // compute new velocity dots[i].dx += (DELTAT * accel.X); dots[i].dy += (DELTAT * accel.Y); // stop dead so it doesn't jitter when nearly still if (Math.abs(dots[i].dx) < STOPVEL && Math.abs(dots[i].dy) < STOPVEL && Math.abs(accel.X) < STOPACC && Math.abs(accel.Y) < STOPACC) { dots[i].dx = 0; dots[i].dy = 0; } // move to new position dots[i].X += dots[i].dx; dots[i].Y += dots[i].dy; // get size of window var height, width; if (isNetscape) { height = window.innerHeight + window.pageYOffset; width = window.innerWidth + window.pageXOffset; } else { height = document.body.clientHeight + document.body.scrollTop; width = document.body.clientWidth + document.body.scrollLeft; } // bounce off 3 walls (leave ceiling open) if (dots[i].Y >= height - DOTSIZE - 1) { if (dots[i].dy > 0) { dots[i].dy = BOUNCE * -dots[i].dy; } dots[i].Y = height - DOTSIZE - 1; } if (dots[i].X >= width - DOTSIZE) { if (dots[i].dx > 0) { dots[i].dx = BOUNCE * -dots[i].dx; } dots[i].X = width - DOTSIZE - 1; } if (dots[i].X < 0) { if (dots[i].dx < 0) { dots[i].dx = BOUNCE * -dots[i].dx; } dots[i].X = 0; } // move img to new position dots[i].obj.left = dots[i].X; dots[i].obj.top = dots[i].Y; } } // end code hiding --> </script>