I loved upgrades and gameplay. Northend TD has great potential to grow. If abilities had connection with upgrades like selecting your abilities from upgrade menu, maybe it'd be better. I've faced a minor bug which you can see below. Anyways nice work keep it up!
1 minor bug in menu: add 1 upgrade, click random upgrade in upgrades menu then click added upgrade from upgrades menu, and finally click a random upgrade again from upgrades menu. Green colour applied to multiple upgrades. (actually same thing happens for troops too)