This game was developed for educational purposes for Bit By Bit (http://littlebitbybit.org/\). Worldwide high scores aren't available yet, but based on my personal experience of watching other people play, the current record is 429. Have fun!
The arrow keys scroll up and down. To prevent this, add this line in your event listener, where you handle up/down arrow events:event.preventDefault();
Also please check out my game at https://repl.it/talk/challenge/Space-Runner/12625.