Based on Puzzle Quest: Challenge of the Warlords, GemVenture is similar puzzle game developed for the NES by Tom Livak for the PDRoms Coding Competition in 2009.

You fight against a series of monsters by swapping adjacent gems. Each match of 3 or more gems of the same color increases your mana, and special heart and spike gems heal you and/or hurt your opponent. Press select to cast spells using the mana you've gained. Your opponent will then take a turn matching gems, and you continue back and forth until only one is left standing. Defeat your opponent and level up your attributes before taking on the next foe. GemVenture features 6 character classes, 18 spells, and 20 monsters, each with their own characteristics.