Hello everyone! I've made couple changes to the game according to feedback from friends and comments. This post will go over each change.

• Number of waves increased to 26 waves to fit new mechanics and new enemies.

• Game can now be sped up or down using the left and right arrow keys. Game speed can be set between 0x and 2.5x speed. Speed can be incremented or decremented at 0.5 intervals. 
• Health regeneration rate is now displayed next to the health text. Although health is a floating point number, the health text will still display a complete integer.
• All buildings now have health. If a building is damaged, a health bar will appear above it to display the remaining HP. Once the HP reaches 0, the building will be destroyed. For now, health can only be replenished when a building is upgraded. I will probably add a 'repair' option in a later update. 

• Forests now upgrade by themselves after a wave is cleared, but can't be manually upgraded.  Forests can be upgraded up to Tier 5. Tier 1 - 0.025 HP regeneration per second. Tier 2 - 0.05 HP regeneration per second. Tier 3 - 0.075 HP regeneration per second. Tier 1 - 0.1 HP regeneration per second. Tier 5 - 0.15 HP regeneration per second. 

• Factories now causes the planet to lose 0.2 HP per second. Each fire rate buff that a turret receives has diminishing returns. My plan for all buildings was to have specific trade off's besides the buy cost. The factory's trade off was straight forward to come up with since it emits smog that should harm the planet. I plan to add trade off's for other buildings as I continue to add new mechanics and building types.
• The UFO's attack has changed to a damaging cone. Once it gets close enough to the planet, it will turn on the damaging cone which deals damage over time. If it detects a forests, it will stay above it until it is destroyed. My plan for the UFOs was for it to target 'resource' type buildings so that it can harm the player's income and buff-providing buildings.

• 'Spaceship' enemy has been added. It will only target turrets and shoots homing missiles over time. I haven't figured out how to properly orient the model to face the direction of movement, so sometimes it will fly around at odd angles. Sorry :(

• There will be a new 'Planet' type enemies. There will be enemy planets with its own hostile turrets that will target your planet. Currently, there is only 1 planet enemy. For now, they appear at the last couple waves of the 26 waves. I'm excited to create more planet type enemies that will use a wide variety of weapons in the future.

For those who tried out the first version of the game, thank you so much for playing and leaving feedback. I hope you will enjoy the new changes! I will try to regularly update the game with new features. If you have any ideas for features, please let me know!

Plans for future updates:

• 'Resouce' building types that generates currency.
• A debuff building that slows down incoming enemies.
• New 'planet' and 'alien' type enemies.
• Boss enemies.
• Repair option for buildings.
• Expanding planet size.
• Procedural difficulty.
• City building aspects (ex. building a colony).