Take a look at your employment contract (you'll need this anyway when you talk to a lawyer). Many contracts will have clauses about outside work/IP rights etc. The enforcement of these clauses depend on your location (and to some extent Google's). To that end, it would be useful to mention approximately where you're based (NYC, CA, Seattle, etc), especially to garner useful lawyer recommendations.

If/when you do moonlight, make sure that you do NOT use company assets to do so. Do NOT use your corporate issue laptop or your corporate email. Typically anything created using company assets is considered company-owned. Also anything that directly competes with Google is dicey.