Cool concept idea! I played the game a few times before reading the description text, so I went in without knowing what to expect.
Now, I'm going to tell you the story of my experience playing FPS with Dice - in hopes it inspires some more ideas as you continue development.
In the first room, after shooting the giant die and breaking it up into multiple dice, I tried to go through the door, but it didn't seem to work, and thought, "Oh, I need to shoot the dice to roll them and make it add up to the number on the wall!" I did that and tried to go through the door again, but it didn't work. So I figured I must have missed something...
I refreshed the browser to try again, and this time I realized that I didn't need to shoot the dice I could go straight into the door. Upon entering the second room, I quickly died. xD So, I refreshed the page once more, this time doing much better and almost completing the second level.
Since I still hadn't read the description text, I wondered if the dice had changed the number of hit points the enemies had or how much damage they dealt.
Finally, I read the description text and see that your intention is to have the dice add player and enemy buffs and just haven't implemented it yet. I'm delighted you submitted the game anyway! Done is better than perfect :-)
All that to say, I had fun and see lots of opportunities to taking this idea further.