App.js

import React, { Component } from 'react'
import logo from './logo.svg'
import './App.css'

import { Route, Link, Redirect } from './Zero'

const paths = [ 'one', 'two', 'three' ]

class App extends Component {
  render() {
    return (
      <div className="App">
        <div className="App-header">
          <h1>Zero Router</h1>
        </div>
        <ul>
          {paths.map(path => (
            <li><Link href={'/'+path}>{path}</Link></li>
          ))}
        </ul>
        <Route path="/">
          {(match) => match.exact ? (
            <Redirect to="/one"/>
          ) : null}
        </Route>
        {paths.map(path => (
          <Route path={'/'+path}>
            {(match) => match && (
              <h2>{path}</h2>
            )}
          </Route>
        ))}
      </div>
    );
  }
}

export default App

ZeroRouter.js

import React, { Component } from 'react'

const instances = []

const register = (comp) => instances.push(comp)

const unregister = (comp) => {
  instances.splice(instances.indexOf(comp), 1)
}

const push = (path) => {
  history.pushState({}, null, path)
  instances.forEach(instance => instance.forceUpdate())
}

const replace = (path) => {
  history.replaceState({}, null, path)
  instances.forEach(instance => instance.forceUpdate())
}

const defaultMatch = (path, url) => {
  const match = new RegExp(`^${path}`).exec(url)
  return match ? {
    url: match[0],
    exact: match[0] === path
  } : null
}

class Route extends Component {
  componentWillMount() {
    addEventListener('popstate', this.handlePop)
    register(this)
  }

  handlePop = () => {
    this.forceUpdate()
  }

  componentWillUnmount() {
    unregister(this)
    removeEventListener('popstate', this.handlePop)
  }

  render() {
    const {
      path,
      children,
      // could pass in a `match` that extracts params
      // with path-to-regexp if you wanted to
      match = defaultMatch
    } = this.props
    return children(match(path, location.pathname))
  }
}

const isModifiedEvent = (event) =>
  !!(event.metaKey || event.altKey || event.ctrlKey || event.shiftKey)

class Link extends Component {
  handleClick = (event) => {
    const { onClick, target, replace, href } = this.props
    if (onClick)
      onClick(event)

    if (
      !event.defaultPrevented && // onClick prevented default
      event.button === 0 && // ignore right clicks
      !target && // let browser handle "target=_blank" etc.
      !isModifiedEvent(event) // ignore clicks with modifier keys
    ) {
      event.preventDefault()
      if (replace) {
        replace(href)
      } else {
        push(href)
      }
    }
  }

  render() {
    return <a {...this.props} onClick={this.handleClick}/>
  }
}

class Redirect extends Component {
  componentDidMount() {
    (this.props.push ? push : replace)(this.props.to)
  }

  render() {
    return null
  }
}

export { Route, Link, Redirect, push, replace }

I mean ... you really do though, and it's not big anymore, this is just a fun little prototype.