Indie developers are the starving artists of the video-game world, often brilliant and innovative, but also misunderstood, underfunded and more prone to writing free-form poetry on their LiveJournals. We at Joystiq believe no one deserves to starve, and many indie developers are entitled to a fridge full of tasty, fulfilling media coverage, right here. This week, Spencer Nielsen describes the benefits of simple mechanics with his iOS title Invader Zurp, a simple tap game with a deep, visually appealing strategy.



What's your game called and what's it about?

The game is a physics-based shooter called Invader Zurp. You play as Zurp (or formally "Zurp: Destroyer of Worlds"), a little alien critter tasked with raining down mighty destruction from planet to planet on his spaceship. You fly on a rail in first person toward structures made of blocks. By touching the screen you fire super-intelligent smart bombs that home in on buildings, defense turrets and incoming missiles. The "touch to shoot" mechanic is dead simple to pick up but there is a deeper strategy in balancing offense, defense and taking measured risks.

Why develop independently, rather than work for an established company?

The freedom to work on ideas I find interesting and be the person that calls the shots is the reason I left Apple after five years to work on my own projects. Being one part of a large team working on large projects was satisfying and rewarding in its own way but I would always get these crazy ideas that I wanted to explore. The ability to see my own vision through and ship these "crazy ideas" has a reward and personal fulfillment that I value more than a steady paycheck.

What inspired you to make Invader Zurp?

I was working on a physics-based multiplayer strategy game called Cannonade and the game wasn't resonating with my testers. In Cannonade the players design castles out of blocks and take turns shooting at each other until one side is completely destroyed. One day I was playing Fruit Ninja and I started thinking about what elements made it a such a hit. In Fruit Ninja there is just one, easy-to-pick-up, well-implemented game mechanic. It's wrapped in great production values and then repeated thousands of times.

I thought to myself: "Does Cannonade have a single, fun mechanic that I could repeat over and over?" The mechanic of "smash your friend's castle" was really fun and satisfying. What if I reduced that down to just "smash castles" and repeated it thousands of times? After a week I had a quick prototype. I knew I had something fun when my "debugging" play sessions started lasting longer than they needed to be. I decided to put Cannonade on hold and flesh out this new game concept into a full-fledged game.

How do you turn such a simple mechanic into a complete, engaging game?

Once I found a mechanic that was genuinely fun, I needed to find a reason to motivate the player to keep playing. I spent a lot of time tweaking the progression of the difficulty curve and adding aspects that allowed the player to influence their own power curve. The player rakes in huge points by making difficult shots like mid-air hits. These points automatically upgrade the attributes of the player's ship. A better ship allows the player to get even more points and the cycle compounds on itself. By giving the player ways to grow more powerful based on their skill, I was able to find a way to take the base gameplay mechanic and add an incentive for players to get better at it and feel the satisfaction of progression.

Will you ever try to complicate the controls or story of Invader Zurp?

I was wary of adding complication without vetting how it would affect the game as a whole. I was afraid that any new addition might run the risk of messing with the core gameplay I had already finely tuned. I eventually settled on what you currently see in the game but I have thought about adding one more element like a special ability/weapon. I am going to experiment around and see if adding this would add to or detract from the game as a whole. I do want to feature the main character more in the game. I feel like there is a really fun story to be explored there.

What's the coolest aspect of Invader Zurp?

Hands down, watching the blocks explode, collapse and sail through the air with realistic physics and beautiful particle effects is the coolest, most satisfying aspect of Invader Zurp. After upgrading your ship to higher levels you feel super powerful as you use your fingers to conduct a symphony of physics destruction. I spent a ton of time optimizing usage of the Bullet Physics Library so that the simulation would run at a decent rate even on older hardware.

You see a lot of 2D physics games in the App Store (mostly puzzlers) but not a whole lot of 3D physics games and even less physics-based shooters. This makes Invader Zurp a truly unique experience that you wont see replicated in any other game.

Anything you'd do differently?

I think I would spend more time on fleshing out the character and story. Right now the focus is completely on the gameplay and I feel that there are a lot of really fun ways that I could work Zurp into the game more.

How big was the team behind Invader Zurp?

For the most part it was just me. I had one friend compose the background music for the stages. I also had two other friends contribute some character art and stage backgrounds.

Do you see yourself as part of a larger indie movement?

I am so new on the scene that I haven't really identified myself with any particular indie ideal or philosophy. All I know is that I stand for making truly unique and creative gaming experiences.

Sell Invader Zurp in one sentence:

Invader Zurp: Conduct a symphony of destruction with your fingers in a physics-based 3D shooter.

What's next?

I have pretty aggressive plans for Invader Zurp updates. I want to include content and features in every update along with the usual bug fixes. One of the most exciting features I have coming up is adding the editor I used to make all the structures in the game and allowing players to construct and upload their own designs to have them included in gameplay.


Invader Zurp is available for iOS devices for $2 -- not such a bad price for taking over every world, ever.

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This article was originally published on Joystiq.