Submitted by @Rutin, the Tower Defense Challenge is your next GameDev Challenge. Create a tower defense strategy game that meets the minimum requirements. 

From the Wikipedia description, Tower defense games have these common gameplay elements:

• territories or possessions (or collectively the "base") that must be defended by the player
• the base must survive waves of multiple incoming "enemy" attacks
• placement of "Tower" elements, or obstructions along the path of attacking enemies

Typical features include:

• Player placed obstructions that can damage or kill enemy attackers before destroying the base
• Ability to repair obstructions
• Ability to upgrade obstructions
• Some sort of currency with which to purchase upgrades and repairs (this can be time, in game currency or experience points, such as being earned by the defeat of an attacking unit
• Enemies capable of traversing multiple paths
• Each wave usually has a set number and types of enemies

Challenge Requirements

The game must have:

• Menu menu and a way to return to the main menu
• Tower defense gameplay mechanics
• Score system
• Game over screen
• Winner screen
• Audio: 1 music track and/or sound effects (firing, enemies being hit, etc)
• Game may be in 2D or 3D

Gameplay Requirements

• At least 1 map/level
• 20 different waves
  • Waves can be same sprites or mix of sprites
  • Waves need to differ in some way - speed, health, abilities, different enemies, etc
  • Must have a Boss wave to end the level
• Point system awards per enemy killed and wave completed
• Player/base health reduced for each enemy that reaches the end of the path
• Towers
  • 5 or more possible towers to build with the possibility to upgrade each tower
  • Towers can be built anywhere outside the moving path
  • Must be a way to prevent player from blocking the maze

Dates

The official Challenge period starts on April 23, 2018 and ends on July 7, 2018.

Submission

Create a new topic in the GameDev Challenge Group Forum as a submission announcement and include:

• Link to project posted for download in GameDev Projects 
  • Upload your files to the project so other members can download and play
  • Please contact me if your submission is a web-based game
• Screenshots should be included on the GameDev Project page and/or the Gallery Album for your project. Embedding screenshots in the topic announcement is encouraged.
  • Embedding YouTube or Vimeo trailers is also encouraged
• A small post-mortem in a GameDev.net Blog associated with your GameDev Project (select Project when posting blog), where you can share what went right, what went wrong, or just share a nifty trick you learned
• Source-code link is encouraged for educational purposes
  • Github link, zip download in GameDev Project, or otherwise

Challenge Award

Participants who complete the challenge and submit it will receive the Tower Defense award in their profiles: