Fewer misclicks when the door is getting hit

Three checks are enough

1. Before: door health, level, price, how much money you have.
2. During: only upgrade, repair, or an item you already own.
3. After: close the panel, see if health or level actually changed.

This is fewer misclicks, not a promise the door takes no damage, and there is no “must keep X coins” or “upgrade after two hits” rule.