Try it here. (may take 1 minute or so to load due to free hosting limitations)
If you know anything about Japanese pitch accent this game should be fairly self explanatory. Note that odaka (尾高) pitch accent words have been removed programmatically from the base dictionary to avoid ambiguity with heiban (平板) words.
If not, the short explanation is that Japanese words have pitch accent with is either flat or drops after a certain part of the word. This can be quite hard to hear if you are not a musician nor come from a language that uses pitch accent to distinguish words. See Wikipedia for in an depth discussion.
I made this game in an attempt to help train my ear for the sound, as well as solidify some basic concepts that I've learned about React and CSS-in-JS. As such, the code is sloppy at times, but I learned a lot about how React works in the process.
The audio is provided through Japanese Pod 101 and the word dictionary based on Kanjium under Creative Commons license.