Thanks for playing and the feedback.
We need to revisit our settings screen. Not all of them are designed in a way that works while the game is active. We've had enough comments asking about it in various jams that we need to make changes so more of them are available from pause. We added the Game Speed slider to the pause screen on one of our other games, and liked it so much that it is now something we plan to do for any game where it doesn't break the gameplay.
One of the shooting enemies has a longer range than most towers. You need to use the longer range towers, such as the starting catapult, to deal with them. We will see if we can better convey this to the player.
We need to rebalance everything, and make upgrading feel more worth the cost.
We had plans for the resources that didn't make it in, so the current number is excessive for the gameplay. I also wanted to add some UI elements to help with them that did not make it in in time. In the post-jam update you will only start to see new resources once you have some of them. We also plan to do some highlighting to draw the eye to the right resources when placing a tower.
The Shield Tower takes the damage instead of any protected towers, as long as the shield is active. Once it takes enough damage the shield goes down, but it also regenerates over time. Repair Towers repair/heal other towers in range that have already been damaged. One is preventative, while the other is reactive.