Thank you for trying to play our game. This is a demo version of the game, we will definitely refine it, release an update with new levels, with new enemies. Improvements really don't work for stone towers, otherwise there would be no point in other towers). In the future, we will disable the ability to install improvements for this type of tower, or we will come up with separate unique improvements for it. As for the fact that the towers don't reach the gates that need to be protected, you can buy bases in the upper-right corner that improve all the towers, and you can also place a base that increases the radius of the towers, and you can also upgrade these bases. There are also upgrades that increase the damage of the towers and their rate of fire. With these upgrades, you can try to complete the game using only archer towers or only magic towers. However, all enemies have different vulnerabilities to magic and physical damage.In future updates, we will add information about enemies so that players can understand how to destroy them more effectively.