Ikaruga is a vertical shmup published and developed by Treasure. It was first released on arcade and Dreamcast, then on a series of other platforms (GameCube, XBLA, Android, Steam). Its gameplay and scoring system uses a polarity mechanic. The present TAS uses the GameCube version as it features the most accurate emulated console. The goal is to get the highest score possible.

Ikaruga's gameplay centers primarily around the polarity mechanic. Only bullets of an opposite polarity can kill the player. Same-color bullets are absorbed and converted into energy for the game's special weapon, a homing laser. Switching the ship's polarity also changes the color of the ship's bullets, and shooting an enemy using opposite-polarity bullets will cause double damage. Killing an enemy using same-polarity bullets triggers suicide bullets toward the player.

In hard mode, killing an enemy using opposite-polarity bullets also triggers suicide bullets, but in half quantity. Moreover, some enemies fire bullets only in hard mode, and bosses have tougher bullet patterns. Overall, hard mode features more bullets, so eventually a higher score.

Ikaruga scoring system relies mainly on its chain system. A chain is completed when three enemies of the same color are shot in a row. The first chain gives the player 100 points, and each subsequent chain gives double points (200, 400, etc.) until the 9th chain (called max chain) which gives 25600 points. After that, each following chain gives 25600 points. If a chain is broken, the chain value starts at 100 points again. The chain status restarts at the beginning of each stage.

On a 2 players mode, each player has its own chain status. Because of this incremental chain value, it is theoretically better to give all chains to one player. For exemple, 20 chains on 1 player is 100+200+...+12800+25600*12=332700 points, but giving 10 chains to player 1 and 10 chains to player 2 yields 2*(100+200+...+12800+25600*2)=153400 points. However, in most chapters, having 2 players allows to get more chains that is possible with one player, so that both players must kill a minimum number of enemies anyway. Only in chapter 5, player 2 gets all possible chains without lowering the total number of chains.

Players can absorb bullets of the same color, and it yields 100 points for almost every type of bullet. Exceptions are the big spheres in the beginning of chapter 4 (500 points), electrical-type bullets in the chapter 4 mid-boss and end of chapter 5 (300 points) and homing lasers of the chapter 5 boss (1000 points). Also, lasers on chapter 3 gives 100 points per frame, making a very good source of points.

Points are granted for firing enemies, and the amount is directly linked to the quantity of health removed. So whatever the way you killed the enemy, you will get the same amount of points. As (almost) every enemy is killed in the present TAS, this scoring part is rarely important. This is used during boss fights mainly, as for example the two pods on chapter 1 boss are vulnerable a few seconds before the main target, so they can be scored.

Points are given at the end of a boss. Each player is given 10,000 times the number of seconds remaining. For chapters with mid-bosses, the number of seconds remaining of each mid-boss/boss are summed up. Because only the integer part of the second is considered, the last second of the fight can be leeched by waiting the last frame of the second before killing the boss. Except for the chapter 5 boss, it gives a higher score to kill the boss as fast as possible.

Each player receives an extend after 3,000,000 points, then every 5,000,000 points. At the end of the game, 500,000 points are given for every extend remaining for each player.

Here is a comparison against the best known 2 players unassisted scores. All the best scores are on the normal difficulty as it is the most popular one. Being on hard difficulty instead of normal only makes a significant difference in chapter 5, during the leeching of the boss. Also, XBLA scores were not incorporated because a few differences in the level design in this version allow higher scores (in chapter 2 and 3 at least). As a side note, scores done by VTF-INO are actually double play (one person controlling the two ships)!

Nach: Extremely impressive run, doing the impossible. Despite being hard to always follow the action (at least for me), the two players shielding each other was a pleasure to behold. Very nice precision showing off what TASing is all about. This run can be improved slightly by skipping the Battle Reports, but in any case, the in-game play was terrific, and the feedback was fantastic. Accepting to stars.

RGamma: Publishing...

feos: Praise CPP! https://github.com/CasualPokePlayer/dolphin/releases/tag/4600S