<ADD: stealth kill component><MOD: add collideCategory to sensor to void collisions between them>
<MOD: add collision group to CatController to avoid collision between characters>
<ADD: Stealth kill>
<ADD: can attack now>
<ADD: ai can attack you now>
<MOD: fix bug of ignoring platform>
<TODO: 1. tidy body.Tag and collisionGroup 2. tidy sensor>
<MOD: Refactor sensors>
<MOD: Attach Mechanism>