When you start the game scene sometimes there is a bug where your character has 0hp
To solve this :
1. Refresh the page.
If this doesn't work:
2. Close the page and open it again.
If THAT doesn't work:
3. Restart browser
IF THAT DOESN'T WORK:
4. Add a new account to your metamask wallet, and either transfer funds from your other account or use a faucet