The original version of Defend Your Castle is a Macromedia Flash-based browser game. It requires the player to kill all enemy units before they destroy the player's castle. There are various ways of accomplishing this, such as picking up enemies and throwing them into the air or attacking them with an array of weapons, which are purchased with points gained from the previous level. Players may also use points to repair or fortify their castle.

The original version of Defend Your Castle is a Macromedia Flash-based browser game. It requires the player to kill all enemy units before they destroy the player's castle. There are various ways of accomplishing this, such as picking up enemies and throwing them into the air or attacking them with an array of weapons, which are purchased with points gained from the previous level. Players may also use points to repair or fortify their castle.