• Learn more about Unity's Visual Effects Graph

• Designing Enemy spawning pacing and mechanics

• One week to complete - shooting for less than 24 - 36 hours.

Finding the Fun

I was motivated to design a simple shooter to blast away at viruses - more of a therapeutic desire than a game design exercise. I wanted it to feel like you were inside the bloodstream as the viruses were invading. I quickly created a shooting mechanic where the targets popped on screen and you had to shoot as many as you could before they filled up the space.

It was tempting to explore more complex mechanics of moving through the space as you took aim and fired at the invading targets, but I wanted to keep it simple - just using the mouse to aim and shoot. This had a very satisfying feeling - not especially interesting - but satisfying. A key to providing a challenge was to ramp up spawn rates and introduce a power up resource in the form of a vaccine that takes out a large percentage of the viruses if you activate it.

Programming the mechanic

The main programming challenge is to create a system for spawning the resources needed - in this case the viruses. I set up 5 spawn points that gradually activated over time. Each spawn point has a random range to spawn a virus. The combination of the random ranges per spawn point and having each one activate over time game me a nice way to increase the spawning of the viruses as time progressed.

Game Loop

I set up 3 levels - level 1 increasing the spawn rates of the virus, level 2 introduces a twist- a random spawn (1 in 4 chance) of a "mutated" virus that would split into 2 viruses when initially hit - this along with a gradual increase in spawn rate gave level 2 a heightened sense of drama. The last level features a boss battle - the "mega virus" appears and now you need to hit it with many shots. Hit count intervals spawn new viruses that "break off" from the mega virus and begin to move towards the players character make it more challenging.

Tuning

Tuning the spawn rates and and timing the power ups was the largest block of time spent on the game.

Polishing

Once the core game play felt good, I started adding materials and art assets including visual effects and audio.