"The Agent of Force – Mars" is unaffected by Spell Cards just like "Guardian Kay'est" and "The Legendary Fisherman".
Vs. "Reverse Trap", "The Agent of Force – Mars"' ATK & DEF become zero but cannot go below zero.
If "The Agent of Force – Mars" attacks "Reflect Bounder", "Reflect Bounder" deals damage based on "The Agent of Force – Mars"' current ATK, so if it has 2000 ATK, then "Reflect Bounder" inflicts 2000 damage; then recalculate "The Agent of Force – Mars"' ATK before performing damage calculation.
When your face-down Defense Position "The Agent of Force – Mars" is attacked, its DEF is increased BEFORE damage calculation.