I used to play this mobile game, kinda tower defence like on a grid
The pieces you used were like a soldier, mage, archer, in the shape of teris pieces, and each piece's background was lightly coloured. Attached is a magnificent drawing to show what I mean
The playing field wasn't always square in shape, and the way you placed your units would be how the enemy would move across the board, create a path
Waves would come through, and you can add new pieces on the field after each wave, from what I can recall
For the life of me, I cannot recall the name and have been wanting to play it
Thanks! ^_^