DragonBox Elements is an amazing mobile (iOS/Android) app that helps teach students about Geometry through Game Based Learning. The way this works is by having players travel through a magical world by solving logic based puzzles in over 100+ levels. The Euclidian concepts covered are: shapes, triangles, angles, and more. This is a very fun game designed for MS/HS aged students and has high replay value.
I highly recommend checking out DragonBox Elements by clicking here!!!
Below is a brief demo video...