zepto.qsa = function(element, selector){
  var found,
      maybeID = selector[0] == ‘#‘,
      maybeClass = !maybeID && selector[0] == ‘.‘,
      nameOnly = maybeID || maybeClass ? selector.slice(1) : selector, // Ensure that a 1 char tag name still gets checked
      isSimple = simpleSelectorRE.test(nameOnly)
  return (isDocument(element) && isSimple && maybeID) ?
    ( (found = element.getElementById(nameOnly)) ? [found] : [] ) :
    (element.nodeType !== 1 && element.nodeType !== 9) ? [] :
    slice.call(
      isSimple && !maybeID ?
        maybeClass ? element.getElementsByClassName(nameOnly) : // If it‘s simple, it could be a class
        element.getElementsByTagName(selector) : // Or a tag
        element.querySelectorAll(selector) // Or it‘s not simple, and we need to query all
    )
}

$.fn.on = function(event, selector, data, callback, one){
  var autoRemove, delegator, $this = this
  if (event && !isString(event)) {
    $.each(event, function(type, fn){
      $this.on(type, selector, data, fn, one)
    })
    return $this
  }

  if (!isString(selector) && !isFunction(callback) && callback !== false)
    callback = data, data = selector, selector = undefined
  if (isFunction(data) || data === false)
    callback = data, data = undefined

  if (callback === false) callback = returnFalse

  return $this.each(function(_, element){
    if (one) autoRemove = function(e){
      remove(element, e.type, callback)
      return callback.apply(this, arguments)
    }

    if (selector) delegator = function(e){
      var evt, match = $(e.target).closest(selector, element).get(0)
      if (match && match !== element) {
        evt = $.extend(createProxy(e), {currentTarget: match, liveFired: element})
        return (autoRemove || callback).apply(match, [evt].concat(slice.call(arguments, 1)))
      }
    }

    add(element, event, callback, data, selector, delegator || autoRemove)
  })
}

function add(element, events, fn, data, selector, delegator, capture){
  var id = zid(element), set = (handlers[id] || (handlers[id] = []))
  events.split(/\s/).forEach(function(event){
    if (event == ‘ready‘) return $(document).ready(fn)
    var handler = parse(event)
    handler.fn = fn
    handler.sel = selector
    // emulate mouseenter, mouseleave
    if (handler.e in hover) fn = function(e){
      var related = e.relatedTarget
      if (!related || (related !== this && !$.contains(this, related)))
        return handler.fn.apply(this, arguments)
    }
    handler.del = delegator
    var callback = delegator || fn
    handler.proxy = function(e){
      e = compatible(e)
      if (e.isImmediatePropagationStopped()) return
      e.data = data
      var result = callback.apply(element, e._args == undefined ? [e] : [e].concat(e._args))
      if (result === false) e.preventDefault(), e.stopPropagation()
      return result
    }
    handler.i = set.length
    set.push(handler)
    if (‘addEventListener‘ in element)
      element.addEventListener(realEvent(handler.e), handler.proxy, eventCapture(handler, capture))
  })
}

function compatible(event, source) {
  if (source || !event.isDefaultPrevented) {
    source || (source = event)

    $.each(eventMethods, function(name, predicate) {
      var sourceMethod = source[name]
      event[name] = function(){
        this[predicate] = returnTrue
        return sourceMethod && sourceMethod.apply(source, arguments)
      }
      event[predicate] = returnFalse
    })

    if (source.defaultPrevented !== undefined ? source.defaultPrevented :
        ‘returnValue‘ in source ? source.returnValue === false :
        source.getPreventDefault && source.getPreventDefault())
      event.isDefaultPrevented = returnTrue
  }
  return event
}