(function() {

  window.main = function() {
    var height, ot, ship, svg, width;
    width = 960;
    height = 500;
    svg = d3.select('body').append('svg').attr('width', width).attr('height', height);
    ship = {
      x: width / 2,
      y: height / 2,
      v: 0,
      a: 0,
      dir: 0,
      vdir: 0
    };
    svg.selectAll('.ship').data([ship]).enter().append('circle').attr('class', 'ship').attr('r', 16);
    d3.select('body').on('keydown', function(e) {
      if (d3.event.keyCode === 38) ship.a += 1;
      if (d3.event.keyCode === 40) ship.a -= 1;
      if (d3.event.keyCode === 39) ship.vdir += 1;
      if (d3.event.keyCode === 37) return ship.vdir -= 1;
    });
    d3.select('body').on('keyup', function(e) {
      if (d3.event.keyCode === 38) ship.a -= 1;
      if (d3.event.keyCode === 40) ship.a += 1;
      if (d3.event.keyCode === 39) ship.vdir -= 1;
      if (d3.event.keyCode === 37) return ship.vdir += 1;
    });
    ot = new Date().getTime();
    return d3.timer(function() {
      var dt, t;
      t = new Date().getTime();
      /* delta in seconds
      */
      dt = (t - ot) / 1000.0;
      ot = t;
      ship.v += Math.min(ship.a * dt * 50, 100);
      ship.dir += ship.vdir * dt;
      ship.x += ship.v * dt * Math.cos(ship.dir);
      ship.y += ship.v * dt * Math.sin(ship.dir);
      svg.selectAll('.ship').attr('cx', function(d) {
        return d.x;
      }).attr('cy', function(d) {
        return d.y;
      });
      return false;
    });
  };

}).call(this);