It isn't completely hacker proof but at least you'll make them work for their 100 lives.
Minor, excellent protection is not the first aim in game development. Let me write some statistics (only as the example):
Sony Vegas was protected with Base32 + Custom + ECDSA-113/ECC-89 -- WAS KEYGENNED by DI team
vTask Studio was protected with online check -- WAS KEYGENNED by TSRh team
HDDlife Pro was protected with nanomites -- WAS CRACKED by ...don't remember
Malwarebytes Antimalware was protected with hash and blacklisting -- WAS KEYGENNED by CRD team
Runtime Revolution Studio was protected with serial number in Virtual Machine -- WAS KEYGENNED by EDGE team
Multi Password Recovery was protected with Themida (the strongest protector!) -- WAS CRACKED by Ismail
Macro Mania was protected with registry key ckecking -- WAS CRACKED by CHiCNCREAM team
What does it mean? Almost any good game will be cracked. If not by keygenning, then by patching. If not by patching, then by loader. If not by loader, then by ... leaching. It's possible to buy a license to learn a protection scheme. Voil?!
Code a nice game - and I (or somebody else) will buy it. People don't buy protections, they buy emotions, feelings...etc.
and...price should be reasonably low.