i really don't remember what my towers looked like at the beginning lol. i built the general path for the fieldrunners to follow, and gradually filled up spaces with mortars and upgraded them. i had more flamethrowers and teslas at the beginning too, but replaced them all. this is the earliest screenshot i have, probably around round 450ish:
Selling really hurts your score so the game penalizes you in that way. I haven't ever used this strategy but it can obviously be very powerful.
LOL....I was about to kill myself after 399...it get so repretative. But you don't always have to play on easy