i should be working right now, so you get some more input from me
usually in Towerdefenses there is a grid for placing Towers (mages). As your map is not really big, i think it will not take a lot of memory if u store which position is free, and where you can not build. For initial blocking you could for instance load some kind of binary texture.
What i think greatly increases the fun of such games is:
- special abilities for enemies (short invulvernability, boss with speed aura, etc)
- a large set of different towers (combining towers for towers with new abilites, giving items to towers for increasing their stats (attackspeed, dmg, and so on)
- special abilities on towers (reduce armor, chain-lightning, critical strike, stun, buffing near towers for a short time and so on (the more, the better, even if there's just little difference between the abilities))
- some kind of rock-paper-scissors system (enemies have different armor types, towers have different attack-types)
- promoting towers which get a lot of kills (just a little increase in their stats)
- something you can do while the waves of enemies are running (if you play for longer time it will get boring to just watch the enemies running down the road.)
- a lot of different visual effects. I really love it when there's a lot going on on my monitor.
What also makes TowerDefenses a bit more interesting are multiplayer modes, where eather your can play together with a friend and/or against someone (meaning you can send some extra enemies to the next wave, what costs some gold aswell)
That's just some ideas that came into my mind for helping you increasing the gameplay-fun
Looking forward to your next update.