Some criticism:
1. The intro is too long
2. Readability is bad because of the pixel-font. This makes reading the long intro even more difficult
3. No need to ask if the player wants to load from checkpoint on every death. 95% he will
4. Sometimes it asks to reload to checkpoint a it after you've already reloaded. I suspect this happens when several enemies kill you at the same time
5. It's getting boring with time
6. It lags in WebGL. WebGL usually works slower, but it also usually runs smooth with simple graphics like this one.