Pinch to zoom. Drag to scroll. Double tap to reset.
Build / upgrade while paused.
Gun tower is not effective against fast enemies. Laser tower is.
Longest path is not always the best option. Towers kill enemies.
Create choke points. Slow tower + Mortar/Rocket tower = Dead enemies.
Level 3 upgrade is expensive but definitely worth it.
Damage enemies early with splash damage.
Sell level 0 towers without loss.
Replace weak towers with more powerful ones.
Fully upgraded slow tower has significantly increased range.
Pause when upgrading in dangerous situation.
Too easy? Try later levels on HARD difficulty ;-)