Thomas Iu

Game Designer





nucleon_01 nucleon_02

Nucleon Game on Xbox Live Marketplace

Nucleon Design Document

Nucleon is an XNA game I made with a team during a Game Jam for UC Irvine Video Game Developers Club. My team had to make a game in one week, based on the theme of "electricity." We later worked to refine the gameplay, and it is now available on Xbox Live Arcade.

This is a survival/defense game in which the player is an electron that can turn into a lightning bolt to blast swarms of invading radiation particles, trying to stop them from colliding with the atomic nucleus.

I was a game designer, level designer, and producer on this game.

My Work On This Game:

  • Collaborated with design team to design game

  • Managed development team to create vertical slice in 1 week

  • Designed player's lightning leap attack to move player around the level and make full use of the environment

  • Designed player's neutron barrier defense to encourage player tactical awareness of weak spots in their defense

  • Wrote documentation specifying game design

  • Designed enemy wave patterns for visual appeal and player challenge

  • Designed some enemy wave patterns to let player easily chain-kill many in one attack to feel powerful and gain rewards

  • Scripted enemy wave spawns and behaviors in C#

  • Specified player properties and enemy difficulty progression to create engaging combat

  • Balanced rate of player earning helpful rewards to establish appropriate challenge

  • Wrote player instruction text

  • Cooperated with programming, art, and audio teams to implement features

  • Edited and selected audio


Lead Designer Craig Brown came up with the original idea for the game, which was to have the player electron fly around and shoot a chain lightning bolt that would be automatically pulled toward enemies in a sequence in order of proximity until eventually pulled into the wall and grounded if the wall was closer than any remaining enemies. The player would be immune to attack, but enemies would approach the atomic nucleus and damage it upon collision. Most of the gameplay is based on this and other ideas Craig proposed.

My primary contribution to the game design was the realization that under the original design, the player would never have to move away from the center of the screen where the nucleus was, since that was the best place to fire lighting to hit the largest number of enemies. I then proposed we have the player transform into the lightning bolt instead of firing it as a projectile. This has the gameplay effect of forcing the player to be pulled to the wall with each attack and then struggle to get far enough from the wall in time to make an effective attack against other incoming enemies. It causes the player to actually move around and make use of the game space, and adds tension to a game that might have otherwise lacked it. From a narrative perspective, this solution also worked out well, since it felt more appropriate for an electron to actually become lightning rather than shoot a lightning projectile. I also came up with a plan for how to create art assets to actually support this visual effect.

My other high level design contribution was proposing that each particle in the nucleus have its own collision, with the neutrons surrounding the proton and acting as a destructible barrier around it. The player would lose if enemies got past the neutrons and struck the proton. Previously, the plan was to have the entire nucleus be a single entity with health points. The feature I proposed made it so that the player would never feel safe from having a large amount of health. If just a couple enemies collided with neutrons on the same side of the nucleus, there would be enough of a gap in the neutrons for the proton to be threatened. The effect of this new feature is to increase tension and add a tactical reason for the player to favor defending one side of the screen over others, depending on the situation.

There are 3 enemy types in the game, each with its own distinctive behavior for the player to anticipate and respond to. Having three choices or three possibilities to evaluate is the minimum number necessary to give players some sense of variety. These 3 types often attack together in combination, so players must rapidly analyze how to fight them and determine priority of attack.

The yellow enemy is most obviously threatening, moving toward the player's atomic core in a straight line. The blue enemy gradually spirals toward the core, seemingly non-threatening but easy to lose track of while occupied elsewhere. The orange enemy moves randomly and very quickly, but with a bias for approaching the core. The randomness of the orange makes it start off moving in non-threatening ways, the player is always wary of it since it can suddenly dart to attack the core faster than the player can respond.

In designing the difficulty progression, I ensured that when all three enemy types attack together in the same wave, the oranges are always faster than the yellows, and the yellows always approach the center faster than the blues. As the game progresses, enemy speed overall increases to challenge the player. However, the speed relationship between the three enemy types remains the same so that players can properly evaluate their relative threat.

I designed the orange enemy's bias for approaching the core to be high enough to be threatening. I set the frequency at which the orange chooses a new direction to be low enough that players can still predict where it will move in the near future.

I designed the player's movement speed to be fast enough to feel responsive, but slow enough that it is challenging to properly reposition to fire again after a poorly timed shot.

I make it easier for the player's kills to earn neutron barriers near the start of the game. This makes the beginning manageable for new players while also clearly demonstrating how the player's kills earn the neutrons. After the first few waves, the game requires far more kills to earn additional neutrons, partly to increase difficulty, and partly to compensate for the rising enemy spawn rate making it easier to earn neutrons through chain kills.

After a point, the difficulty progression ceases to increase spawn rate, and focuses more on increasing enemy speed. The reason for this is that putting too many enemies on screen just makes them vulnerable to the player's chain-kills and does not necessarily increase game difficulty.

However, in some cases I purposefully spawn very large numbers of enemies in puzzle waves. Players must figure out the tactic to deal with these large swarms. Such waves require either quick reflexes or precise timing and positioning to survive. Failure usually means instant loss since the player likely lacks sufficient neutron barriers to block all the enemies. Success in the challenge rewards the player in massive chain-kills that look visually awesome, pump up the player's score, and help earn valuable neutron barriers. These visually distinctive waves test the player's understanding of the combat system and mark milestones in progress through the game.

In designing and scripting the puzzle waves, I tried to make them very intimidating, but also very satisfying to overcome. I make the player feel barely in control and very close to death during the wave, so that survival brings a feeling of relief and triumph. The randomness of the orange enemy makes it unsuitable for the carefully scripted puzzle waves, so I only used it for 1 of them.

Some puzzle waves frequently allow the player enough chain-kills to rapidly recharge the super attack. These waves require use of the super attack to survive, and test the player's ability to choose when to use it. Good performance in these waves usually rewards the player with a fully charged super meter to use in the next wave.

As producer, I managed the team's efforts during production. Craig later took on more of the producer's role when we were making the final changes to ensure the game met specifications for publishing on Xbox Live Arcade. Although I managed the team as a whole, I more closely directed the artists and audio designer, while Lead Programmer Johnny Huynh directly supervised the programmers.