The Premise
Doodle Defender is a fixed-screen shooter in which the player must survive an onslaught of enemies as they descend toward the bottom of the page. The entire game takes place within the mind of a student scribbling in their notebook; they are the hero of the story, imagining that they are the pilot of a spaceship defending the planet.
Here you can see one of my initial sketches of the game mechanics from early in the brainstorming process.
The Inspiration
Gameplay for Doodle Defender was inspired by arcade classics like Space Invaders and Galaga, with modest graphics and easy-to-learn mechanics, but still challenging and enjoyable.
Player sprite sheet
Enemy sprite sheet
The Aesthetic
My goal with Doodle Defender was to make it as visually simplistic as possible to cut down on production time for artwork. All assets were hand drawn by me and imported into the game. This includes the player, enemies, main menu elements, and other assets.
Most assets were drawn 2-3 times to create variations in the line art; I then turned these different images into sprite sheets to add a jittery, sketchy animation to the assets.
The Gameplay
Gameplay is centered around a basic idea: the player and enemies shoot back and forth in an effort to destroy one another. However, there are a few mechanics that bring more excitement to the firefight:
The Barrier: the barrier blocks all enemy projectiles while still allowing the player to shoot through it, but it can be destroyed over time.
Frenzy Mode: once the barrier has been taken down, enemies will go into a frenzy; they will both shoot and move faster until the barrier has regenerated.
Powerups: powerup items will occasionally float across the screen; if shot by the player, they grant temporary boosts like a stronger projectile, faster movement, or an extra life.
Balancing and Iteration
A key piece of feedback I received was that the player object originally wasn't fun to control. I had used physics features within Unity to try to make the movement of the ship feel realistic, but it just ended up making it more difficult to control and therefore less fun. I updated the player movement and restricted them to only one axis, using clear boundaries and simple controls to make the experience more enjoyable.
Looking at the images below, you can see that the initial sketch on the left had a different style for the barrier as opposed to the final version on the right.
The original concept for the barrier
The final in-game version of the barrier
Because I was implementing a feature I had never used before, I also went through several iterations of how the barrier mechanic functioned.
Iteration 1: The barrier can be destroyed once its health is depleted, but it doesn't come back.
Drawbacks: This made the game much too challenging for the player, leaving them with little-to-no defenses very early on.
Iteration 2: The barrier can be destroyed, but regenerates after 5 seconds. While the barrier is still there, new enemies can't spawn and enemies on the screen stop moving.
Drawbacks: The enemies not moving when the barrier was there lessened the sense of urgency and made the gameplay too easy. From a technological standpoint, it was also difficult to get enemies to behave appropriately when it came to stopping and starting movement.
Iteration 3: When the barrier is still intact, enemies that collide with it are destroyed and no points are earned. Enemies will still advance regardless of if the barrier is there or not. When the barrier has been destroyed, they increase their speed and fire rate to create a momentary burst of difficulty for the player.
The third iteration is what I finally settled on, leading to the addition of the "Frenzy Mode" mechanic as well. While it wasn't necessarily perfect, it did cover most of what I wanted to achieve as far as the gameplay experience.
