To upgrade a tower, tap on it and then tap on the upgrade icon. Upgrading a tower increases its attack power, range, and rate of fire. It is important to constantly upgrade your towers to keep up with the increasing difficulty of the levels. However, keep in mind that upgrading a tower costs gold, which is earned by defeating enemies. So, you need to find a balance between building new towers and upgrading existing ones.

One of the unique features of Cartoon Defense 4 is the ability to summon cartoon characters to assist you in battle. These characters have special skills that can turn the tide of a battle. To summon a character, tap on the character icon at the bottom of the screen and then tap on an empty spot on the map. Each character has a cooldown period, so use them strategically to maximize their effectiveness.

As you progress through the game, you will unlock more towers, characters, and power-ups. It is important to experiment with different combinations of towers and characters to find the best strategy for each level. Some enemies are resistant to certain types of damage, so you need to adapt your strategy accordingly.

In addition to the main gameplay, Cartoon Defense 4 also provides various side quests and challenges to keep you engaged. These quests may require you to defeat a certain number of enemies, earn a certain amount of gold, or protect a specific tower. Completing these quests rewards you with gold, gems, and other valuable resources that can be used to strengthen your defenses.

Another aspect of Cartoon Defense 4 is the introduction of a skill tree. As you progress through the game, you earn skill points that can be used to unlock and upgrade various skills. These skills provide passive bonuses to your towers, characters, and overall gameplay. It is important to invest your skill points wisely to maximize your performance in battle.

Now that we have covered the basics, let's discuss some strategies and tips to help you beat every level in Cartoon Defense 4. Firstly, it is important to have a strong defense at the beginning of a level. Build multiple towers near the entrance of the map to quickly eliminate enemies before they reach your castle. Consider using characters with area damage abilities to clear out large groups of enemies.

Secondly, pay close attention to the path the enemies follow. Some levels have multiple paths, and it is important to place your towers strategically to cover all possible routes. Additionally, consider using towers with long-range attacks near junctions or chokepoints to maximize their effectiveness.

Thirdly, always keep an eye on your resources. Gold is essential for building towers and upgrading them, so make sure you have enough income to sustain your defenses. If you find yourself running low on gold, consider selling some of your low-level towers and replacing them with stronger ones.

Lastly, don't forget to use your characters' skills. They can be a game-changer in difficult situations. For example, some characters have healing abilities that can restore health to your towers, while others have crowd control abilities that can temporarily immobilize enemies. Experiment with different combinations of characters and their skills to find the best strategy for each level.

In conclusion, Cartoon Defense 4 is a challenging and addictive tower defense game that requires strategic thinking and careful planning. By following the tips and strategies provided in this walkthrough, you should be able to beat every level and progress smoothly through the game. Remember to constantly upgrade your towers, experiment with different combinations of towers and characters, and use your skills wisely. Good luck and have fun defending your castle!