Very fun and a good idea! I like the idea of upgrades based on arcade power-ups. I think you've done a great job in a lot of areas, and the concept is pretty unique!
Here's a list of my thoughts and feedback after unlocking everything and playing for a bit
- I think the "Active Charge" power-up should either be more frequent or removed altogether. Your active already charges very quickly when facing groups of zombies, but it doesn't charge at all when fighting the tank for the most part. You could instead base the charge on damage done/hits instead of enemies killed.
- Similarly the starter tank's heal is very powerful as a quickly charged active, making it much better than the other two. During the story mode, I barely lost and health and what I did lose was quickly replenished.
- The Scout train's weapons in general could feel a bit better. The auto-cannon is solid as a primary, but it could do with a little more splash damage. It's very reliable against big targets that are up close though! The canister, on the other hand, doesn't really sell the fantasy of a giant shotgun. When only one pellet hits a zombie, they don't even die. The fairly narrow spread and lack of pellets makes clearing groups difficult sometimes too. Finally, the grenade is much weaker than the starter tank's healing, and doesn't do a ton of damage compared to how hard it is to land sometimes. As an active weapon that you (currently) can only use about once per boss fight, it's both underwhelming (doing about 3-4 auto-cannon shots worth of damage) and hard to land, given the projectile drop.
- I think the starter tank is great, no notes. Solid weapons and an arguable overpowered ability.
- The heavy assault, my beloved; the heavy machine gun feels great, and I like that it can punch above it's weight. The howitzer is very fun, though I feel like it should have an even larger cool-down but with a silly amount of splash damage. Make it really feel like a strategic choice, because the heavy machine gun does better DPS almost always. In that same vein, I think the artillery strike should have more of a realistic delay, but be more impactful. More splash damage/better targeting would be nice! It's also currently pretty much useless against cars or bosses as far as I can tell. I still love this train though.
Some other things I noticed/bugs
- When I destroyed a windmill near a river, the ground under the windmill kinda "height-mapped" to the base of the windmill's debris. It's hard to explain, but it basically stopped conforming to the uneven terrain of the riverbed as soon as it was destroyed.
- Not sure if this is intended, but endless mode seems to have less power-ups than the story (making it more difficult, especially since I got less health power-ups) and the second boss I got was two tanks and once plus cars, which was significantly harder than just one tank!
- There is no visible timer for the fire-rate power-up. When I first got one, I couldn't even tell whether it was permanent or not. A small timer on the screen would help ease that confusion.
- The zombies themselves could be a little easier to see against the background. I like what you're doing with the green heads, so maybe make more of them a bright green or the red/fleshy theme you've got going on with the vehicles.
Overall, I'm excited to see how this project progresses and what you make next! I also enjoyed your other game, though it's very different from this one!