Stronghold the Moving Fortress [YGLD-ENC39] Common

Special Summon this card in Defense Position as an Effect Monster (Machine-Type/EARTH/Level 4/ATK 0/DEF 2000). (This card is also still a Trap Card.) While you control a "Green Gadget", "Red Gadget", and "Yellow Gadget", this card gains 3000 ATK.