@damage_mods

This is an array of the percentages that are added together to determine the final damage. If the hit is made on a marker, the corresponding percentage is added to the final damage calculation. Also note that the closer the hit is to the center of a marker the greater the damage dealt, and by being very close to the center bonus damage is dealt.

@markers

This is an array of the length of each bar in the set of markers. The total should add up to the length of the main bar, which in this case is 600.

@keys

This is an array of the keys that are to be pressed to make a hit when a marker is active.

@actor_attack_data[id] = [...]
@actor_data[actor_id] = [...]
@skill_data[skill_id] = [...]

Replace actor_id or skill_id with the id of the actor or skill that the data should apply to.
For @actor_data[actor_id] = [...], replace the ... with the id's used in @actor_attack_data seperated by commas.

These lines define the data for each actor or skill. The elements are as follows:
[Max Wait, Wait Increment, Damage Mod, Keys, Targets, Markers]

Max Wait - A number like 1000 (recommended)
Wait Increment - Another number like 20 (20 or lower recommended)

1000 / 20 = 50 Frames. So it takes 50 frames for the bar to fill. This is pretty quick, and does not allow much time to react.

Damage Mod - @damage_mods[index]. Where the index is the element of the array to be used as the hit timing data.
EX @damage_mods[1] = [33,33,33]
The average of each marker is worth 33% in this case. A hit in the very center of a marker would result in an aditional 33% damage.

Keys - @keys[index]. Where the index is the element of the array to be used as the target keys.
EX @keys[1] = [a,b,c]
The key combination for this setup is the A, B and C buttons (or Z, X, and C)

Targets - @targets[index]. Where the index is the element of the array to be used as the target images.
EX @targets[1] = [target_z,target_x,target_c]
The images shown for the key combination are "target_z", "target_x", and "target_c"

Markers - @markers[index]. Where the index is the element of the array to be used as the marker images.
EX @markers[1] = [200,200,200]

Using Custom Images
There are four images in the pictures folder. Feel free to edit them to your liking (I tried to make them simple to understand). The system makes calculations based on the width of each image, so different things can be changed by changing the with of the images. For example: in the demo project, the "marker_on" and "marker_off" images are short, giving the player just a little time to hit them. If you made both of the images bigger, then the player would have more time to hit the markers. The same applies to changing the size of the target.

Aliased methods:
Game_Battler:: attack_effect
Game_Battler:: skill_effect
Scene_Battle:: start_phase4
Scene_Battle:: update_phase4_step3

Version 1.30:

• Rearranged the script (again), to make it a little easier to read/modify
  
• Included the option for a DDR style bar (from Rayn's suggestion), which can bee seen by playing the demo

Version 1.20:

• Changed the inner workings, so that changes made durring runtime are saved when the game is saved
  
• You can now change the attacks for each actor through a one line event script (Ex in the demo)
  
• Cleaned up the script a bit more

Version 1.10:

• The bar system calculates the placement of the marker bars so you don't have to
  
• Actors can be set up to select a "random" pattern for the bar, when using an attack
  
• Changed the images used for the bars.
  
• Cleaned up the script a bit

Version 1.01:

• Changed the usage for specifying bar usage. Skills and characters do not require the use of a bar.
  
• Removed dependency on Scene_Battle:: update_phase4_step6.
  
• Added status effect to weapons, depending on accuracy