diff --git a/README.md b/README.md
index d4b5194..c347847 100644
--- a/README.md
+++ b/README.md
@@ -295,6 +295,79 @@ curl http://127.0.0.1:8080/such_path
 > such_path
 ```
 
+## Implementing Your Own Router
+
+Implementing a custom path matching library on top of this module is as easy as using `Router.Engine`. For example, to implement an "exact" path matching module, we can do this:
+
+```js
+var Engine = require('router').Engine
+var slice = Array.prototype.slice
+
+/**
+ * Accepts the path and some options we defined in our engine.
+ */
+function toFunction (route, options) {
+  if (!options.end) {
+    return function (path) {
+      var matches = path.substr(0, route.length) === route
+
+      return matches ? { path: path } : false
+    }
+  }
+
+  return function (path) {
+    return path === route ? { path: path } : false
+  }
+}
+
+/**
+ * The constructor must return the engine instance.
+ */
+function ExactRouter (options) {
+  return Engine.call(this, options)
+}
+
+/**
+ * Inherits from the engine prototype.
+ */
+ExactRouter.prototype = Object.create(Engine.prototype)
+
+/**
+ * Set up `Router#use` with our custom path matching implementation.
+ */
+ExactRouter.prototype.use = function () {
+  // Use a simple utility for supporting a single path argument like `router`.
+  var opts = Router.Engine.sanitizeArgs.apply(null, arguments)
+  var match = toFunction(opts.path, { end: false })
+
+  return Engine.prototype.use.call(this, opts.path, match, opts.callbacks)
+}
+
+/**
+ * Set up `Router#route` with our custom path patching implementation.
+ */
+ExactRouter.prototype.route = function (path) {
+  var match = toFunction(path, { end: true })
+
+  return Engine.prototype.route.call(this, path, match)
+}
+
+/**
+ * Set up all the router method shorthands.
+ */
+Engine.methods.forEach(function (method) {
+  ExactRouter.prototype[method] = function (path) {
+    var route = this.route(path)
+    route[method].apply(route, slice.call(arguments, 1))
+    return this
+  }
+})
+```
+
+Both the path matching function and the path itself must be passed into the `route` and `use` engine methods. This is for debugging, so `path` should be a human-readable path name. `Engine#use` also accepts an array of handlers to immediately include. The match function must return an object of `{ path: string, params: object }` or `false` if it didn't match.
+
+Note: The path matching utility should not throw errors. Decoding of parameters is handled by the engine.
+
 ## License
 
 [MIT](LICENSE)
diff --git a/engine.js b/engine.js
new file mode 100644
index 0000000..6213f49
--- /dev/null
+++ b/engine.js
@@ -0,0 +1,763 @@
+/*!
+ * router
+ * Copyright(c) 2013 Roman Shtylman
+ * Copyright(c) 2014 Douglas Christopher Wilson
+ * MIT Licensed
+ */
+
+/**
+ * Module dependencies.
+ * @private
+ */
+
+var debug = require('debug')('router')
+var flatten = require('array-flatten')
+var methods = require('methods')
+var mixin = require('utils-merge')
+var parseUrl = require('parseurl')
+var setPrototypeOf = require('setprototypeof')
+var Layer = require('./lib/layer')
+var Route = require('./lib/route')
+
+/**
+ * Module variables.
+ * @private
+ */
+
+var slice = Array.prototype.slice
+var allmethods = methods.concat('all')
+
+/* istanbul ignore next */
+var defer = typeof setImmediate === 'function'
+  ? setImmediate
+  : function(fn){ process.nextTick(fn.bind.apply(fn, arguments)) }
+
+/**
+ * Expose `Router`.
+ */
+
+module.exports = Engine
+module.exports.Route = Route
+module.exports.sanitizeArgs = sanitizeArgs
+module.exports.methods = allmethods
+
+/**
+ * Initialize a new `Router` with the given `options`.
+ *
+ * @param {object} options
+ * @return {Router} which is an callable function
+ * @public
+ */
+
+function Engine(options) {
+  var opts = options || {}
+
+  function router(req, res, next) {
+    router.handle(req, res, next)
+  }
+
+  // inherit from the correct prototype
+  setPrototypeOf(router, this)
+
+  router.mergeParams = opts.mergeParams
+  router.params = {}
+  router.stack = []
+
+  return router
+}
+
+/**
+ * Engine prototype inherits from a Function.
+ */
+
+Engine.prototype = Object.create(Function.prototype)
+
+/**
+ * Map the given param placeholder `name`(s) to the given callback.
+ *
+ * Parameter mapping is used to provide pre-conditions to routes
+ * which use normalized placeholders. For example a _:user_id_ parameter
+ * could automatically load a user's information from the database without
+ * any additional code.
+ *
+ * The callback uses the same signature as middleware, the only difference
+ * being that the value of the placeholder is passed, in this case the _id_
+ * of the user. Once the `next()` function is invoked, just like middleware
+ * it will continue on to execute the route, or subsequent parameter functions.
+ *
+ * Just like in middleware, you must either respond to the request or call next
+ * to avoid stalling the request.
+ *
+ *  router.param('user_id', function(req, res, next, id){
+ *    User.find(id, function(err, user){
+ *      if (err) {
+ *        return next(err)
+ *      } else if (!user) {
+ *        return next(new Error('failed to load user'))
+ *      }
+ *      req.user = user
+ *      next()
+ *    })
+ *  })
+ *
+ * @param {string} name
+ * @param {function} fn
+ * @public
+ */
+
+Engine.prototype.param = function param(name, fn) {
+  if (!name) {
+    throw new TypeError('argument name is required')
+  }
+
+  if (typeof name !== 'string') {
+    throw new TypeError('argument name must be a string')
+  }
+
+  if (!fn) {
+    throw new TypeError('argument fn is required')
+  }
+
+  if (typeof fn !== 'function') {
+    throw new TypeError('argument fn must be a function')
+  }
+
+  var params = this.params[name]
+
+  if (!params) {
+    params = this.params[name] = []
+  }
+
+  params.push(fn)
+
+  return this
+}
+
+/**
+ * Dispatch a req, res into the router.
+ *
+ * @private
+ */
+
+Engine.prototype.handle = function handle(req, res, callback) {
+  if (!callback) {
+    throw new TypeError('argument callback is required')
+  }
+
+  debug('dispatching %s %s', req.method, req.url)
+
+  var idx = 0
+  var methods
+  var protohost = getProtohost(req.url) || ''
+  var removed = ''
+  var self = this
+  var slashAdded = false
+  var paramcalled = {}
+
+  // middleware and routes
+  var stack = this.stack
+
+  // manage inter-router variables
+  var parentParams = req.params
+  var parentUrl = req.baseUrl || ''
+  var done = restore(callback, req, 'baseUrl', 'next', 'params')
+
+  // setup next layer
+  req.next = next
+
+  // for options requests, respond with a default if nothing else responds
+  if (req.method === 'OPTIONS') {
+    methods = []
+    done = wrap(done, generateOptionsResponder(res, methods))
+  }
+
+  // setup basic req values
+  req.baseUrl = parentUrl
+  req.originalUrl = req.originalUrl || req.url
+
+  next()
+
+  function next(err) {
+    var layerError = err === 'route'
+      ? null
+      : err
+
+    // remove added slash
+    if (slashAdded) {
+      req.url = req.url.substr(1)
+      slashAdded = false
+    }
+
+    // restore altered req.url
+    if (removed.length !== 0) {
+      req.baseUrl = parentUrl
+      req.url = protohost + removed + req.url.substr(protohost.length)
+      removed = ''
+    }
+
+    // no more matching layers
+    if (idx >= stack.length) {
+      defer(done, layerError)
+      return
+    }
+
+    // get pathname of request
+    var path = getPathname(req)
+
+    if (path == null) {
+      return done(layerError)
+    }
+
+    // find next matching layer
+    var layer
+    var match
+    var route
+
+    while (!match && idx < stack.length) {
+      layer = stack[idx++]
+      match = layer.match(path)
+      route = layer.route
+
+      if (!match) {
+        continue
+      }
+
+      if (!route) {
+        // process non-route handlers normally
+        continue
+      }
+
+      var method = req.method;
+      var has_method = route._handles_method(method)
+
+      // build up automatic options response
+      if (!has_method && method === 'OPTIONS' && methods) {
+        methods.push.apply(methods, route._methods())
+      }
+
+      // don't even bother matching route
+      if (!has_method && method !== 'HEAD') {
+        match = false
+        continue
+      }
+    }
+
+    // no match
+    if (!match) {
+      return done(layerError)
+    }
+
+    var layerPath = match.path
+    var layerParams = decodeLayerParams(match.params)
+
+    if (layerParams instanceof Error) {
+      return done(layerParams)
+    }
+
+    // store route for dispatch on change
+    if (route) {
+      req.route = route
+    }
+
+    // Capture one-time layer values
+    req.params = self.mergeParams
+      ? mergeParams(layerParams, parentParams)
+      : layerParams
+
+    // this should be done for the layer
+    self.process_params(match, paramcalled, req, res, function (err) {
+      if (err) {
+        return next(layerError || err)
+      }
+
+      if (route) {
+        return layer.handle_request(req, res, next)
+      }
+
+      trim_prefix(layer, layerError, layerPath, path)
+    })
+  }
+
+  function trim_prefix(layer, layerError, layerPath, path) {
+    var c = path[layerPath.length]
+
+    if (c && c !== '/') {
+      next(layerError)
+      return
+    }
+
+     // Trim off the part of the url that matches the route
+     // middleware (.use stuff) needs to have the path stripped
+    if (layerPath.length !== 0) {
+      debug('trim prefix (%s) from url %s', layerPath, req.url)
+      removed = layerPath
+      req.url = protohost + req.url.substr(protohost.length + removed.length)
+
+      // Ensure leading slash
+      if (!protohost && req.url[0] !== '/') {
+        req.url = '/' + req.url
+        slashAdded = true
+      }
+
+      // Setup base URL (no trailing slash)
+      req.baseUrl = parentUrl + (removed[removed.length - 1] === '/'
+        ? removed.substring(0, removed.length - 1)
+        : removed)
+    }
+
+    debug('%s %s : %s', layer.name, layerPath, req.originalUrl)
+
+    if (layerError) {
+      layer.handle_error(layerError, req, res, next)
+    } else {
+      layer.handle_request(req, res, next)
+    }
+  }
+}
+
+/**
+ * Process any parameters for the layer.
+ *
+ * @private
+ */
+
+Engine.prototype.process_params = function process_params(match, called, req, res, done) {
+  var params = this.params
+
+  // captured parameters from the layer, keys and values
+  var keys = match.params && Object.keys(match.params)
+
+  // fast track
+  if (!keys || keys.length === 0) {
+    return done()
+  }
+
+  var i = 0
+  var name
+  var paramIndex = 0
+  var key
+  var paramVal
+  var paramCallbacks
+  var paramCalled
+
+  // process params in order
+  // param callbacks can be async
+  function param(err) {
+    if (err) {
+      return done(err)
+    }
+
+    if (i >= keys.length ) {
+      return done()
+    }
+
+    paramIndex = 0
+    key = keys[i++]
+
+    if (!key) {
+      return done()
+    }
+
+    paramVal = req.params[key]
+    paramCallbacks = params[key]
+    paramCalled = called[key]
+
+    if (paramVal === undefined || !paramCallbacks) {
+      return param()
+    }
+
+    // param previously called with same value or error occurred
+    if (paramCalled && (paramCalled.error || paramCalled.match === paramVal)) {
+      // restore value
+      req.params[key] = paramCalled.value
+
+      // next param
+      return param(paramCalled.error)
+    }
+
+    called[key] = paramCalled = {
+      error: null,
+      match: paramVal,
+      value: paramVal
+    }
+
+    paramCallback()
+  }
+
+  // single param callbacks
+  function paramCallback(err) {
+    var fn = paramCallbacks[paramIndex++]
+
+    // store updated value
+    paramCalled.value = req.params[key]
+
+    if (err) {
+      // store error
+      paramCalled.error = err
+      param(err)
+      return
+    }
+
+    if (!fn) return param()
+
+    try {
+      fn(req, res, paramCallback, paramVal, key)
+    } catch (e) {
+      paramCallback(e)
+    }
+  }
+
+  param()
+}
+
+/**
+ * Use the given middleware function, with optional path, defaulting to "/".
+ *
+ * Use (like `.all`) will run for any http METHOD, but it will not add
+ * handlers for those methods so OPTIONS requests will not consider `.use`
+ * functions even if they could respond.
+ *
+ * The other difference is that _route_ path is stripped and not visible
+ * to the handler function. The main effect of this feature is that mounted
+ * handlers can operate without any code changes regardless of the "prefix"
+ * pathname.
+ *
+ * @public
+ */
+
+Engine.prototype.use = function use(path, match, handlers) {
+  if (!path) {
+    throw new TypeError('argument path is required')
+  }
+
+  if (!match) {
+    throw new TypeError('argument match is required')
+  }
+
+  if (typeof match !== 'function') {
+    throw new TypeError('argument match must be a function')
+  }
+
+  if (handlers.length === 0) {
+    throw new TypeError('argument handler is required')
+  }
+
+  var layerMatch = path === '/' ? null : match
+
+  handlers.forEach(function (fn) {
+    if (typeof fn !== 'function') {
+      throw new TypeError('argument handler must be a function')
+    }
+
+    // add the middleware
+    debug('use %s %s', path, fn.name || '<anonymous>')
+
+    var layer = new Layer(path, layerMatch, fn)
+    layer.route = undefined
+    this.stack.push(layer)
+  }, this)
+
+  return this
+}
+
+/**
+ * Create a new Route for the given path.
+ *
+ * Each route contains a separate middleware stack and VERB handlers.
+ *
+ * See the Route api documentation for details on adding handlers
+ * and middleware to routes.
+ *
+ * @param {function} path
+ * @return {Route}
+ * @public
+ */
+
+Engine.prototype.route = function route(path, match) {
+  if (!path) {
+    throw new TypeError('argument path is required')
+  }
+
+  if (!match) {
+    throw new TypeError('argument match is required')
+  }
+
+  if (typeof match !== 'function') {
+    throw new TypeError('argument match must be a function')
+  }
+
+  var route = new Route(path)
+  var layer = new Layer(path, match, handle)
+
+  function handle(req, res, next) {
+    route.dispatch(req, res, next)
+  }
+
+  layer.route = route
+
+  this.stack.push(layer)
+
+  return route
+}
+
+/**
+ * Generate a callback that will make an OPTIONS response.
+ *
+ * @param {OutgoingMessage} res
+ * @param {array} methods
+ * @private
+ */
+
+function generateOptionsResponder(res, methods) {
+  return function onDone(fn, err) {
+    if (err || methods.length === 0) {
+      return fn(err)
+    }
+
+    trySendOptionsResponse(res, methods, fn)
+  }
+}
+
+/**
+ * Get pathname of request.
+ *
+ * @param {IncomingMessage} req
+ * @private
+ */
+
+function getPathname(req) {
+  try {
+    return parseUrl(req).pathname;
+  } catch (err) {
+    return undefined;
+  }
+}
+
+/**
+ * Get get protocol + host for a URL.
+ *
+ * @param {string} url
+ * @private
+ */
+
+function getProtohost(url) {
+  if (url.length === 0 || url[0] === '/') {
+    return undefined
+  }
+
+  var searchIndex = url.indexOf('?')
+  var pathLength = searchIndex !== -1
+    ? searchIndex
+    : url.length
+  var fqdnIndex = url.substr(0, pathLength).indexOf('://')
+
+  return fqdnIndex !== -1
+    ? url.substr(0, url.indexOf('/', 3 + fqdnIndex))
+    : undefined
+}
+
+/**
+ * Merge params with parent params
+ *
+ * @private
+ */
+
+function mergeParams(params, parent) {
+  if (typeof parent !== 'object' || !parent) {
+    return params
+  }
+
+  // make copy of parent for base
+  var obj = mixin({}, parent)
+
+  // simple non-numeric merging
+  if (!(0 in params) || !(0 in parent)) {
+    return mixin(obj, params)
+  }
+
+  var i = 0
+  var o = 0
+
+  // determine numeric gaps
+  while (i === o || o in parent) {
+    if (i in params) i++
+    if (o in parent) o++
+  }
+
+  // offset numeric indices in params before merge
+  for (i--; i >= 0; i--) {
+    params[i + o] = params[i]
+
+    // create holes for the merge when necessary
+    if (i < o) {
+      delete params[i]
+    }
+  }
+
+  return mixin(parent, params)
+}
+
+/**
+ * Restore obj props after function
+ *
+ * @private
+ */
+
+function restore(fn, obj) {
+  var props = new Array(arguments.length - 2)
+  var vals = new Array(arguments.length - 2)
+
+  for (var i = 0; i < props.length; i++) {
+    props[i] = arguments[i + 2]
+    vals[i] = obj[props[i]]
+  }
+
+  return function(err){
+    // restore vals
+    for (var i = 0; i < props.length; i++) {
+      obj[props[i]] = vals[i]
+    }
+
+    return fn.apply(this, arguments)
+  }
+}
+
+/**
+ * Send an OPTIONS response.
+ *
+ * @private
+ */
+
+function sendOptionsResponse(res, methods) {
+  var options = Object.create(null)
+
+  // build unique method map
+  for (var i = 0; i < methods.length; i++) {
+    options[methods[i]] = true
+  }
+
+  // construct the allow list
+  var allow = Object.keys(options).sort().join(', ')
+
+  // send response
+  res.setHeader('Allow', allow)
+  res.setHeader('Content-Length', Buffer.byteLength(allow))
+  res.setHeader('Content-Type', 'text/plain')
+  res.setHeader('X-Content-Type-Options', 'nosniff')
+  res.end(allow)
+}
+
+/**
+ * Try to send an OPTIONS response.
+ *
+ * @private
+ */
+
+function trySendOptionsResponse(res, methods, next) {
+  try {
+    sendOptionsResponse(res, methods)
+  } catch (err) {
+    next(err)
+  }
+}
+
+/**
+ * Wrap a function
+ *
+ * @private
+ */
+
+function wrap(old, fn) {
+  return function proxy() {
+    var args = new Array(arguments.length + 1)
+
+    args[0] = old
+    for (var i = 0, len = arguments.length; i < len; i++) {
+      args[i + 1] = arguments[i]
+    }
+
+    fn.apply(this, args)
+  }
+}
+
+/**
+ * Attempt to decode layer parameters
+ */
+
+function decodeLayerParams(params) {
+  try {
+    return decodeParams(params)
+  } catch (err) {
+    return err
+  }
+}
+
+/**
+ * Decode all param values
+ *
+ * @param {object} params
+ * @return {object}
+ */
+
+function decodeParams(params) {
+  var decodedParams = {}
+
+  if (params) {
+    Object.keys(params).forEach(function (key) {
+      decodedParams[key] = decodeParam(params[key])
+    })
+  }
+
+  return decodedParams
+}
+
+/**
+ * Decode param value
+ *
+ * @param {string} val
+ * @return {string}
+ * @api private
+ */
+
+function decodeParam(val){
+  if (typeof val !== 'string') {
+    return val
+  }
+
+  try {
+    return decodeURIComponent(val)
+  } catch (e) {
+    var err = new TypeError("Failed to decode param '" + val + "'")
+    err.status = 400
+    throw err
+  }
+}
+
+/**
+ * Helper for sanitizing `Router.prototype.use` arguments.
+ */
+
+function sanitizeArgs(handler) {
+  var offset = 0
+  var path = '/'
+
+  // default path to '/'
+  // disambiguate router.use([handler])
+  if (handler != null && typeof handler !== 'function') {
+    var arg = handler
+
+    while (Array.isArray(arg) && arg.length !== 0) {
+      arg = arg[0]
+    }
+
+    // first arg is the path
+    if (typeof arg !== 'function') {
+      offset = 1
+      path = handler
+    }
+  }
+
+  var callbacks = flatten(slice.call(arguments, offset))
+
+  return { path: path, callbacks: callbacks }
+}
diff --git a/index.js b/index.js
index 8f06c18..1ccded5 100644
--- a/index.js
+++ b/index.js
@@ -1,726 +1,81 @@
-/*!
- * router
- * Copyright(c) 2013 Roman Shtylman
- * Copyright(c) 2014 Douglas Christopher Wilson
- * MIT Licensed
- */
-
 /**
  * Module dependencies.
  * @private
  */
 
-var debug = require('debug')('router')
-var flatten = require('array-flatten')
-var Layer = require('./lib/layer')
 var methods = require('methods')
-var mixin = require('utils-merge')
-var parseUrl = require('parseurl')
-var Route = require('./lib/route')
-var setPrototypeOf = require('setprototypeof')
-
-/**
- * Module variables.
- * @private
- */
-
+var flatten = require('array-flatten')
+var Engine = require('./engine')
+var pathToRegexp = require('./lib/path-to-regexp')
 var slice = Array.prototype.slice
 
-/* istanbul ignore next */
-var defer = typeof setImmediate === 'function'
-  ? setImmediate
-  : function(fn){ process.nextTick(fn.bind.apply(fn, arguments)) }
-
 /**
  * Expose `Router`.
  */
 
 module.exports = Router
+module.exports.Engine = Engine
+module.exports.Route = Engine.Route
 
 /**
- * Expose `Route`.
- */
-
-module.exports.Route = Route
-
-/**
- * Initialize a new `Router` with the given `options`.
- *
- * @param {object} options
- * @return {Router} which is an callable function
- * @public
+ * Construct a router instance.
  */
 
-function Router(options) {
+function Router (options) {
   if (!(this instanceof Router)) {
     return new Router(options)
   }
 
   var opts = options || {}
+  var router = Engine.call(this, opts)
 
-  function router(req, res, next) {
-    router.handle(req, res, next)
-  }
-
-  // inherit from the correct prototype
-  setPrototypeOf(router, this)
-
-  router.caseSensitive = opts.caseSensitive
-  router.mergeParams = opts.mergeParams
-  router.params = {}
   router.strict = opts.strict
-  router.stack = []
+  router.caseSensitive = opts.caseSensitive
 
   return router
 }
 
 /**
- * Router prototype inherits from a Function.
+ * Inherits from the router engine.
  */
 
-/* istanbul ignore next */
-Router.prototype = function () {}
-
-/**
- * Map the given param placeholder `name`(s) to the given callback.
- *
- * Parameter mapping is used to provide pre-conditions to routes
- * which use normalized placeholders. For example a _:user_id_ parameter
- * could automatically load a user's information from the database without
- * any additional code.
- *
- * The callback uses the same signature as middleware, the only difference
- * being that the value of the placeholder is passed, in this case the _id_
- * of the user. Once the `next()` function is invoked, just like middleware
- * it will continue on to execute the route, or subsequent parameter functions.
- *
- * Just like in middleware, you must either respond to the request or call next
- * to avoid stalling the request.
- *
- *  router.param('user_id', function(req, res, next, id){
- *    User.find(id, function(err, user){
- *      if (err) {
- *        return next(err)
- *      } else if (!user) {
- *        return next(new Error('failed to load user'))
- *      }
- *      req.user = user
- *      next()
- *    })
- *  })
- *
- * @param {string} name
- * @param {function} fn
- * @public
- */
-
-Router.prototype.param = function param(name, fn) {
-  if (!name) {
-    throw new TypeError('argument name is required')
-  }
-
-  if (typeof name !== 'string') {
-    throw new TypeError('argument name must be a string')
-  }
-
-  if (!fn) {
-    throw new TypeError('argument fn is required')
-  }
-
-  if (typeof fn !== 'function') {
-    throw new TypeError('argument fn must be a function')
-  }
-
-  var params = this.params[name]
-
-  if (!params) {
-    params = this.params[name] = []
-  }
-
-  params.push(fn)
-
-  return this
-}
-
-/**
- * Dispatch a req, res into the router.
- *
- * @private
- */
-
-Router.prototype.handle = function handle(req, res, callback) {
-  if (!callback) {
-    throw new TypeError('argument callback is required')
-  }
-
-  debug('dispatching %s %s', req.method, req.url)
-
-  var idx = 0
-  var methods
-  var protohost = getProtohost(req.url) || ''
-  var removed = ''
-  var self = this
-  var slashAdded = false
-  var paramcalled = {}
-
-  // middleware and routes
-  var stack = this.stack
-
-  // manage inter-router variables
-  var parentParams = req.params
-  var parentUrl = req.baseUrl || ''
-  var done = restore(callback, req, 'baseUrl', 'next', 'params')
-
-  // setup next layer
-  req.next = next
-
-  // for options requests, respond with a default if nothing else responds
-  if (req.method === 'OPTIONS') {
-    methods = []
-    done = wrap(done, generateOptionsResponder(res, methods))
-  }
-
-  // setup basic req values
-  req.baseUrl = parentUrl
-  req.originalUrl = req.originalUrl || req.url
-
-  next()
-
-  function next(err) {
-    var layerError = err === 'route'
-      ? null
-      : err
-
-    // remove added slash
-    if (slashAdded) {
-      req.url = req.url.substr(1)
-      slashAdded = false
-    }
-
-    // restore altered req.url
-    if (removed.length !== 0) {
-      req.baseUrl = parentUrl
-      req.url = protohost + removed + req.url.substr(protohost.length)
-      removed = ''
-    }
-
-    // no more matching layers
-    if (idx >= stack.length) {
-      defer(done, layerError)
-      return
-    }
-
-    // get pathname of request
-    var path = getPathname(req)
-
-    if (path == null) {
-      return done(layerError)
-    }
-
-    // find next matching layer
-    var layer
-    var match
-    var route
-
-    while (match !== true && idx < stack.length) {
-      layer = stack[idx++]
-      match = matchLayer(layer, path)
-      route = layer.route
-
-      if (typeof match !== 'boolean') {
-        // hold on to layerError
-        layerError = layerError || match
-      }
-
-      if (match !== true) {
-        continue
-      }
-
-      if (!route) {
-        // process non-route handlers normally
-        continue
-      }
-
-      if (layerError) {
-        // routes do not match with a pending error
-        match = false
-        continue
-      }
-
-      var method = req.method;
-      var has_method = route._handles_method(method)
-
-      // build up automatic options response
-      if (!has_method && method === 'OPTIONS' && methods) {
-        methods.push.apply(methods, route._methods())
-      }
-
-      // don't even bother matching route
-      if (!has_method && method !== 'HEAD') {
-        match = false
-        continue
-      }
-    }
-
-    // no match
-    if (match !== true) {
-      return done(layerError)
-    }
-
-    // store route for dispatch on change
-    if (route) {
-      req.route = route
-    }
-
-    // Capture one-time layer values
-    req.params = self.mergeParams
-      ? mergeParams(layer.params, parentParams)
-      : layer.params
-    var layerPath = layer.path
-
-    // this should be done for the layer
-    self.process_params(layer, paramcalled, req, res, function (err) {
-      if (err) {
-        return next(layerError || err)
-      }
-
-      if (route) {
-        return layer.handle_request(req, res, next)
-      }
-
-      trim_prefix(layer, layerError, layerPath, path)
-    })
-  }
-
-  function trim_prefix(layer, layerError, layerPath, path) {
-    var c = path[layerPath.length]
-
-    if (c && c !== '/') {
-      next(layerError)
-      return
-    }
-
-     // Trim off the part of the url that matches the route
-     // middleware (.use stuff) needs to have the path stripped
-    if (layerPath.length !== 0) {
-      debug('trim prefix (%s) from url %s', layerPath, req.url)
-      removed = layerPath
-      req.url = protohost + req.url.substr(protohost.length + removed.length)
-
-      // Ensure leading slash
-      if (!protohost && req.url[0] !== '/') {
-        req.url = '/' + req.url
-        slashAdded = true
-      }
-
-      // Setup base URL (no trailing slash)
-      req.baseUrl = parentUrl + (removed[removed.length - 1] === '/'
-        ? removed.substring(0, removed.length - 1)
-        : removed)
-    }
-
-    debug('%s %s : %s', layer.name, layerPath, req.originalUrl)
-
-    if (layerError) {
-      layer.handle_error(layerError, req, res, next)
-    } else {
-      layer.handle_request(req, res, next)
-    }
-  }
-}
+Router.prototype = Object.create(Engine.prototype)
 
 /**
- * Process any parameters for the layer.
- *
- * @private
+ * Create a `path-to-regexp` compatible `.use`.
  */
 
-Router.prototype.process_params = function process_params(layer, called, req, res, done) {
-  var params = this.params
-
-  // captured parameters from the layer, keys and values
-  var keys = layer.keys
-
-  // fast track
-  if (!keys || keys.length === 0) {
-    return done()
-  }
-
-  var i = 0
-  var name
-  var paramIndex = 0
-  var key
-  var paramVal
-  var paramCallbacks
-  var paramCalled
-
-  // process params in order
-  // param callbacks can be async
-  function param(err) {
-    if (err) {
-      return done(err)
-    }
-
-    if (i >= keys.length ) {
-      return done()
-    }
-
-    paramIndex = 0
-    key = keys[i++]
-
-    if (!key) {
-      return done()
-    }
-
-    name = key.name
-    paramVal = req.params[name]
-    paramCallbacks = params[name]
-    paramCalled = called[name]
-
-    if (paramVal === undefined || !paramCallbacks) {
-      return param()
-    }
-
-    // param previously called with same value or error occurred
-    if (paramCalled && (paramCalled.error || paramCalled.match === paramVal)) {
-      // restore value
-      req.params[name] = paramCalled.value
-
-      // next param
-      return param(paramCalled.error)
-    }
-
-    called[name] = paramCalled = {
-      error: null,
-      match: paramVal,
-      value: paramVal
-    }
-
-    paramCallback()
-  }
-
-  // single param callbacks
-  function paramCallback(err) {
-    var fn = paramCallbacks[paramIndex++]
-
-    // store updated value
-    paramCalled.value = req.params[key.name]
-
-    if (err) {
-      // store error
-      paramCalled.error = err
-      param(err)
-      return
-    }
-
-    if (!fn) return param()
-
-    try {
-      fn(req, res, paramCallback, paramVal, key.name)
-    } catch (e) {
-      paramCallback(e)
-    }
-  }
-
-  param()
-}
+Router.prototype.use = function use() {
+  var opts = Engine.sanitizeArgs.apply(null, arguments)
 
-/**
- * Use the given middleware function, with optional path, defaulting to "/".
- *
- * Use (like `.all`) will run for any http METHOD, but it will not add
- * handlers for those methods so OPTIONS requests will not consider `.use`
- * functions even if they could respond.
- *
- * The other difference is that _route_ path is stripped and not visible
- * to the handler function. The main effect of this feature is that mounted
- * handlers can operate without any code changes regardless of the "prefix"
- * pathname.
- *
- * @public
- */
-
-Router.prototype.use = function use(handler) {
-  var offset = 0
-  var path = '/'
-
-  // default path to '/'
-  // disambiguate router.use([handler])
-  if (typeof handler !== 'function') {
-    var arg = handler
-
-    while (Array.isArray(arg) && arg.length !== 0) {
-      arg = arg[0]
-    }
-
-    // first arg is the path
-    if (typeof arg !== 'function') {
-      offset = 1
-      path = handler
-    }
-  }
-
-  var callbacks = flatten(slice.call(arguments, offset))
-
-  if (callbacks.length === 0) {
-    throw new TypeError('argument handler is required')
-  }
-
-  callbacks.forEach(function (fn) {
-    if (typeof fn !== 'function') {
-      throw new TypeError('argument handler must be a function')
-    }
-
-    // add the middleware
-    debug('use %s %s', path, fn.name || '<anonymous>')
-
-    var layer = new Layer(path, {
-      sensitive: this.caseSensitive,
-      strict: false,
-      end: false
-    }, fn)
-
-    layer.route = undefined
-
-    this.stack.push(layer)
-  }, this)
+  var match = pathToRegexp(opts.path, {
+    sensitive: this.caseSensitive,
+    strict: false,
+    end: false
+  })
 
-  return this
+  return Engine.prototype.use.call(this, opts.path, match, opts.callbacks)
 }
 
 /**
- * Create a new Route for the given path.
- *
- * Each route contains a separate middleware stack and VERB handlers.
- *
- * See the Route api documentation for details on adding handlers
- * and middleware to routes.
- *
- * @param {string} path
- * @return {Route}
- * @public
+ * Create a `path-to-regexp` compatible route.
  */
 
 Router.prototype.route = function route(path) {
-  var route = new Route(path)
-
-  var layer = new Layer(path, {
+  var match = pathToRegexp(path, {
     sensitive: this.caseSensitive,
     strict: this.strict,
     end: true
-  }, handle)
+  })
 
-  function handle(req, res, next) {
-    route.dispatch(req, res, next)
-  }
-
-  layer.route = route
-
-  this.stack.push(layer)
-  return route
+  return Engine.prototype.route.call(this, path, match)
 }
 
 // create Router#VERB functions
-methods.concat('all').forEach(function(method){
+Engine.methods.forEach(function (method) {
   Router.prototype[method] = function (path) {
     var route = this.route(path)
     route[method].apply(route, slice.call(arguments, 1))
     return this
   }
 })
-
-/**
- * Generate a callback that will make an OPTIONS response.
- *
- * @param {OutgoingMessage} res
- * @param {array} methods
- * @private
- */
-
-function generateOptionsResponder(res, methods) {
-  return function onDone(fn, err) {
-    if (err || methods.length === 0) {
-      return fn(err)
-    }
-
-    trySendOptionsResponse(res, methods, fn)
-  }
-}
-
-/**
- * Get pathname of request.
- *
- * @param {IncomingMessage} req
- * @private
- */
-
-function getPathname(req) {
-  try {
-    return parseUrl(req).pathname;
-  } catch (err) {
-    return undefined;
-  }
-}
-
-/**
- * Get get protocol + host for a URL.
- *
- * @param {string} url
- * @private
- */
-
-function getProtohost(url) {
-  if (url.length === 0 || url[0] === '/') {
-    return undefined
-  }
-
-  var searchIndex = url.indexOf('?')
-  var pathLength = searchIndex !== -1
-    ? searchIndex
-    : url.length
-  var fqdnIndex = url.substr(0, pathLength).indexOf('://')
-
-  return fqdnIndex !== -1
-    ? url.substr(0, url.indexOf('/', 3 + fqdnIndex))
-    : undefined
-}
-
-/**
- * Match path to a layer.
- *
- * @param {Layer} layer
- * @param {string} path
- * @private
- */
-
-function matchLayer(layer, path) {
-  try {
-    return layer.match(path);
-  } catch (err) {
-    return err;
-  }
-}
-
-/**
- * Merge params with parent params
- *
- * @private
- */
-
-function mergeParams(params, parent) {
-  if (typeof parent !== 'object' || !parent) {
-    return params
-  }
-
-  // make copy of parent for base
-  var obj = mixin({}, parent)
-
-  // simple non-numeric merging
-  if (!(0 in params) || !(0 in parent)) {
-    return mixin(obj, params)
-  }
-
-  var i = 0
-  var o = 0
-
-  // determine numeric gaps
-  while (i === o || o in parent) {
-    if (i in params) i++
-    if (o in parent) o++
-  }
-
-  // offset numeric indices in params before merge
-  for (i--; i >= 0; i--) {
-    params[i + o] = params[i]
-
-    // create holes for the merge when necessary
-    if (i < o) {
-      delete params[i]
-    }
-  }
-
-  return mixin(parent, params)
-}
-
-/**
- * Restore obj props after function
- *
- * @private
- */
-
-function restore(fn, obj) {
-  var props = new Array(arguments.length - 2)
-  var vals = new Array(arguments.length - 2)
-
-  for (var i = 0; i < props.length; i++) {
-    props[i] = arguments[i + 2]
-    vals[i] = obj[props[i]]
-  }
-
-  return function(err){
-    // restore vals
-    for (var i = 0; i < props.length; i++) {
-      obj[props[i]] = vals[i]
-    }
-
-    return fn.apply(this, arguments)
-  }
-}
-
-/**
- * Send an OPTIONS response.
- *
- * @private
- */
-
-function sendOptionsResponse(res, methods) {
-  var options = Object.create(null)
-
-  // build unique method map
-  for (var i = 0; i < methods.length; i++) {
-    options[methods[i]] = true
-  }
-
-  // construct the allow list
-  var allow = Object.keys(options).sort().join(', ')
-
-  // send response
-  res.setHeader('Allow', allow)
-  res.setHeader('Content-Length', Buffer.byteLength(allow))
-  res.setHeader('Content-Type', 'text/plain')
-  res.setHeader('X-Content-Type-Options', 'nosniff')
-  res.end(allow)
-}
-
-/**
- * Try to send an OPTIONS response.
- *
- * @private
- */
-
-function trySendOptionsResponse(res, methods, next) {
-  try {
-    sendOptionsResponse(res, methods)
-  } catch (err) {
-    next(err)
-  }
-}
-
-/**
- * Wrap a function
- *
- * @private
- */
-
-function wrap(old, fn) {
-  return function proxy() {
-    var args = new Array(arguments.length + 1)
-
-    args[0] = old
-    for (var i = 0, len = arguments.length; i < len; i++) {
-      args[i + 1] = arguments[i]
-    }
-
-    fn.apply(this, args)
-  }
-}
diff --git a/lib/layer.js b/lib/layer.js
index d1124f9..d2bd71c 100644
--- a/lib/layer.js
+++ b/lib/layer.js
@@ -10,7 +10,6 @@
  * @private
  */
 
-var pathRegexp = require('path-to-regexp')
 var debug = require('debug')('router:layer')
 
 /**
@@ -26,23 +25,16 @@ var hasOwnProperty = Object.prototype.hasOwnProperty
 
 module.exports = Layer
 
-function Layer(path, options, fn) {
+function Layer(path, match, fn) {
   if (!(this instanceof Layer)) {
-    return new Layer(path, options, fn)
+    return new Layer(path, match, fn)
   }
 
   debug('new %s', path)
-  options = options || {}
 
   this.handle = fn
   this.name = fn.name || '<anonymous>'
-  this.params = undefined
-  this.path = undefined
-  this.regexp = pathRegexp(path, this.keys = [], options)
-
-  if (path === '/' && options.end === false) {
-    this.regexp.fast_slash = true
-  }
+  this.match = match || fast_slash
 }
 
 /**
@@ -94,82 +86,6 @@ Layer.prototype.handle_request = function handle(req, res, next) {
   }
 }
 
-/**
- * Check if this route matches `path`, if so
- * populate `.params`.
- *
- * @param {String} path
- * @return {Boolean}
- * @api private
- */
-
-Layer.prototype.match = function match(path) {
-  if (path == null) {
-    // no path, nothing matches
-    this.params = undefined
-    this.path = undefined
-    return false
-  }
-
-  if (this.regexp.fast_slash) {
-    // fast path non-ending match for / (everything matches)
-    this.params = {}
-    this.path = ''
-    return true
-  }
-
-  var m = this.regexp.exec(path)
-
-  if (!m) {
-    this.params = undefined
-    this.path = undefined
-    return false
-  }
-
-  // store values
-  this.params = {}
-  this.path = m[0]
-
-  var keys = this.keys
-  var params = this.params
-  var prop
-  var n = 0
-  var key
-  var val
-
-  for (var i = 1, len = m.length; i < len; ++i) {
-    key = keys[i - 1]
-    prop = key
-      ? key.name
-      : n++
-    val = decode_param(m[i])
-
-    if (val !== undefined || !(hasOwnProperty.call(params, prop))) {
-      params[prop] = val
-    }
-  }
-
-  return true
-}
-
-/**
- * Decode param value.
- *
- * @param {string} val
- * @return {string}
- * @api private
- */
-
-function decode_param(val){
-  if (typeof val !== 'string') {
-    return val
-  }
-
-  try {
-    return decodeURIComponent(val)
-  } catch (e) {
-    var err = new TypeError("Failed to decode param '" + val + "'")
-    err.status = 400
-    throw err
-  }
+function fast_slash () {
+  return { path: '' }
 }
diff --git a/lib/path-to-regexp.js b/lib/path-to-regexp.js
new file mode 100644
index 0000000..6c0523b
--- /dev/null
+++ b/lib/path-to-regexp.js
@@ -0,0 +1,52 @@
+var pathToRegexp = require('path-to-regexp')
+
+module.exports = pathRegexp
+
+function pathRegexp (path, options) {
+  // fast path non-ending match for / (everything matches)
+  if (path === '/' && options.end === false) {
+    return fast_slash
+  }
+
+  var keys = []
+  var regexp = pathToRegexp(path, keys, options)
+
+  return function (pathname) {
+    var m = regexp.exec(pathname)
+
+    if (!m) {
+      return false
+    }
+
+    // store values
+    var path = m[0]
+    var params = {}
+    var prop
+    var n = 0
+    var key
+    var val
+
+    for (var i = 1, len = m.length; i < len; ++i) {
+      key = keys[i - 1]
+      prop = key
+        ? key.name
+        : n++
+      val = m[i]
+
+      if (val !== undefined || !(hasOwnProperty.call(params, prop))) {
+        params[prop] = val
+      }
+    }
+
+    return { path: path, params: params }
+  }
+
+}
+
+/**
+ * Always return true.
+ */
+
+function fast_slash () {
+  return { path: '' }
+}
diff --git a/lib/route.js b/lib/route.js
index 21b325f..52f42fd 100644
--- a/lib/route.js
+++ b/lib/route.js
@@ -12,8 +12,8 @@
 
 var debug = require('debug')('router:route')
 var flatten = require('array-flatten')
-var Layer = require('./layer')
 var methods = require('methods')
+var Layer = require('./layer')
 
 /**
  * Module variables.
@@ -29,7 +29,7 @@ var slice = Array.prototype.slice
 module.exports = Route
 
 /**
- * Initialize `Route` with the given `path`,
+ * Initialize `Route` with the given `path`.
  *
  * @param {String} path
  * @api private
@@ -177,7 +177,7 @@ Route.prototype.all = function all(handler) {
       throw new TypeError('argument handler must be a function')
     }
 
-    var layer = Layer('/', {}, fn)
+    var layer = new Layer('/', null, fn)
     layer.method = undefined
 
     this.methods._all = true
@@ -202,7 +202,7 @@ methods.forEach(function (method) {
 
       debug('%s %s', method, this.path)
 
-      var layer = Layer('/', {}, fn)
+      var layer = new Layer('/', null, fn)
       layer.method = method
 
       this.methods[method] = true
diff --git a/package.json b/package.json
index 9db5c81..a343131 100644
--- a/package.json
+++ b/package.json
@@ -26,6 +26,7 @@
     "LICENSE",
     "HISTORY.md",
     "README.md",
+    "engine.js",
     "index.js"
   ],
   "engines": {
diff --git a/test/engine.js b/test/engine.js
new file mode 100644
index 0000000..a2a241a
--- /dev/null
+++ b/test/engine.js
@@ -0,0 +1,170 @@
+
+var after = require('after')
+var methods = require('methods')
+var Router = require('..')
+var utils = require('./support/utils')
+
+var assert = utils.assert
+var createServer = utils.createServer
+var request = utils.request
+
+describe('Engine', function () {
+  var Engine = Router.Engine
+
+  it('should return a function', function () {
+    assert.equal(typeof Engine(), 'function')
+  })
+
+  it('should return a function using new', function () {
+    assert.equal(typeof (new Engine()), 'function')
+  })
+
+  describe('custom router', function () {
+    var slice = Array.prototype.slice
+
+    function toFunction (route, options) {
+      if (!options.end) {
+        return function (path) {
+          var matches = path.substr(0, route.length) === route
+
+          return matches ? { path: path } : false
+        }
+      }
+
+      return function (path) {
+        return path === route ? { path: path } : false
+      }
+    }
+
+    function ExactRouter (options) {
+      return Engine.call(this, options)
+    }
+
+    ExactRouter.prototype = Object.create(Engine.prototype)
+
+    ExactRouter.prototype.use = function () {
+      var opts = Router.Engine.sanitizeArgs.apply(null, arguments)
+      var match = toFunction(opts.path, { end: false })
+
+      return Engine.prototype.use.call(this, opts.path, match, opts.callbacks)
+    }
+
+    ExactRouter.prototype.route = function (path) {
+      var match = toFunction(path, { end: true })
+
+      return Engine.prototype.route.call(this, path, match)
+    }
+
+    Engine.methods.forEach(function (method) {
+      ExactRouter.prototype[method] = function (path) {
+        var route = this.route(path)
+        route[method].apply(route, slice.call(arguments, 1))
+        return this
+      }
+    })
+
+    describe('.all(path, fn)', function () {
+      it('should respond to all methods', function (done) {
+        var cb = after(methods.length, done)
+        var router = new ExactRouter()
+        var server = createServer(router)
+        router.all('/', helloWorld)
+
+        methods.forEach(function (method) {
+          if (method === 'connect') {
+            // CONNECT is tricky and supertest doesn't support it
+            return cb()
+          }
+
+          var body = method !== 'head'
+            ? 'hello, world'
+            : ''
+
+          request(server)
+          [method]('/')
+          .expect(200, body, cb)
+        })
+      })
+    })
+
+    methods.slice().sort().forEach(function (method) {
+      if (method === 'connect') {
+        // CONNECT is tricky and supertest doesn't support it
+        return
+      }
+
+      var body = method !== 'head'
+        ? 'hello, world'
+        : ''
+
+      describe('.' + method + '(path, ...fn)', function () {
+        it('should respond to a ' + method.toUpperCase() + ' request', function (done) {
+          var router = new ExactRouter()
+          var server = createServer(router)
+
+          router[method]('/', helloWorld)
+
+          request(server)
+          [method]('/')
+          .expect(200, body, done)
+        })
+
+        it('should accept multiple arguments', function (done) {
+          var router = new ExactRouter()
+          var server = createServer(router)
+
+          router[method]('/bar', sethit(1), sethit(2), helloWorld)
+
+          request(server)
+          [method]('/bar')
+          .expect('x-fn-1', 'hit')
+          .expect('x-fn-2', 'hit')
+          .expect(200, body, done)
+        })
+      })
+    })
+
+    describe('.use(...fn)', function () {
+      it('should invoke function for all requests', function (done) {
+        var cb = after(3, done)
+        var router = new ExactRouter()
+        var server = createServer(router)
+
+        router.use(saw)
+
+        request(server)
+        .get('/')
+        .expect(200, 'saw GET /', cb)
+
+        request(server)
+        .options('/')
+        .expect(200, 'saw OPTIONS /', cb)
+
+        request(server)
+        .post('/foo')
+        .expect(200, 'saw POST /foo', cb)
+      })
+    })
+  })
+})
+
+function saw(req, res) {
+  var msg = 'saw ' + req.method + ' ' + req.originalUrl
+  res.statusCode = 200
+  res.setHeader('Content-Type', 'text/plain')
+  res.end(msg)
+}
+
+function helloWorld(req, res) {
+  res.statusCode = 200
+  res.setHeader('Content-Type', 'text/plain')
+  res.end('hello, world')
+}
+
+function sethit(num) {
+  var name = 'x-fn-' + String(num)
+  return function hit(req, res, next) {
+    res.setHeader(name, 'hit')
+    next()
+  }
+}