Congratulations, Henry!
I'm not sure if it's gotten harder, but it is different - more varied. The new towers are fun, but ultimately I seem to get better value out of my usual combination of darts, anti-sircraft, and freeze towers. The new creeps are a pain, the way they keep slipping through diagonal gaps. I experimented with several alternate layouts, but none seemed to work as well as the thin diagonal passages I'd used previously. The new creeps just forced me to develop the backfield earlier than I had previously. I.e. assume they
will get through some cracks, but have enough additional layers in place that there's still time to kill them off before they reach their goals.
The reason it not necessarily harder, in my opinion, is because they no longer have those flying bosses at level 42. Which is kind of disappointing because I
did eventually figure out how to kill them in hard mode in the earlier version of the game. But given that they no longer enter in nice even lines, maybe it's just as well the air bosses were removed. Killing them in hard mode was only possible with very careful positioning - and if the air boss came in at a random position, as seems the norm now, I think it would be very chancy whether the AA guns were in the right position or not. Replacing the air bosses with a squadron is fairer, as we get an averaging-out of the random effects of entry position. Ultimately the total anti-air power necessary to defeat the squadron at level 49 is about the same as was required to defeat the old air bosses at level 42. So maybe it's about the same difficulty as before.
I notice that the score is reduced a bit every time you sell off a
unit. That's annoying. I think this was probably also true in the earlier version of the game, but not documented. The amount of the reduction increases the more times you do it, so the first time you sell something, it subtracts 6 from your score. Then 8, 10... I would do a
lot of moving things around. Now I discover it's penalized. Oh well. Ultimately I'm more interested in getting to the end with all 20 lives; I don't care that much about the score.