I wanted to break down how plays are simulated so that everyone has a better understanding of how to analyze the plays in testing.  As always, feedback and questions are welcome.  I will lock this thread, but feel free to create a new one if you have anything concerning this topic.

A few terms I will be throwing around:

• MATCH UP - this is where we take one or more players from both sides and compare their ratings for a particular action.  For instance, comparing the players blocking at the inside of the line will look at their average inside block rating (a mix of GD ratings) and categorize the offensive advantage/disadvantage.  The range of these will be Great Advantage, Advantage, Slight Advantage, Equal, Slight Disadvantage, Disadvantage, and Great Disadvantage.  The match up also includes the relative degree of where the rating comparison falls within the category, so we can treat someone that barely falls within the Disadvantage range different than one that falls deep within it.
• INFLUENCE - for each match up the players may not be fully invested in the location or action and this can be represented by a percentage.  This would mean a player with less influence in a match up would not contribute his ratings to the mix as much.
• MOMENTUM HITS - this is a numeric value that represents a ball carrier's momentum which in turn is used in several checks where we want to check how much activity the ball carrier has had throughout the rest of the play. For instance, if the player is breaking tackles, then he is slowing down and will be less likely to make moves to avoid tackles.  A player can also gain momentum throughout the play if he is not breaking tackles or easily avoiding tackles, but the Momentum Hits will never go less than 0 as that represent a player at full momentum.
• PLAY REACTION RATING - this is a rating combining GI and Formation IQ that represents how well a player reacts to certain actions within a play and makes decisions based on those actions.

Locations/Areas
The engine plays through the plays moving the ball from location to location, as well as looking at various locations for actions like determining a target for a pass.  They are mostly broken down to represent certain concentrations of defensive players. Here are how the locations break down:

• Very Short: this is the area including the line of scrimmage and behind it.  Broken down to inside and outside.
• Short: 1 - 6 yard area. Broken down to inside and outside.
• Medium: 7-12 yard area
• Long: 13-20 yard area
• Deep: 21+ yard area

Each play from scrimmage will go through the following steps:

• select an offensive play from the offensive team's active playbook for the current down and distance
• select offensive players for each slot
• select the defensive play from the defensive team's active playbook based on the current conditions
• select defensive players for each slot
• determine the offensive play call - rush or pass
• determine the defensive play call - rush or pass defense as well as if there is a blitz
• determine offensive players involved in the play - set ball carrier if a rushing play
• if blitzing, determine which player blitzes
• play through a series of steps (1, 2, 3, ...) moving the ball as the play progresses until the play is called dead.
• update stats for the play and update the current game state to move to the next play

i will expand on the play steps in the following posts, looking at both rushing and passing, as that is where the meat of the play resides.

ANATOMY OF A RUSHING PLAY
This breaks down the actions within each step of a rushing play.  As the play continues, the defense will try to tackle the ball carrier with various factors based on which location the ball carrier is currently in.  If the ball carrier is tackled, the play is dead.  If he is not, then the ball carrier (and ball) move to the next location and repeat.

For each step, movement through each location, the following actions are taken:

• Set players involved based on location.
  • Down field locations
    • Offensive players involvement based on their route distributions and blocking settings.  Blocking players will always be set to block at the line.
    • Defensive players are involved down field based on their role and Line/Cover setting.  Line players, including blitzers, will always be at the line but may follow the ball carrier down field depending on their speed and play reaction.  Safeties will be involved in the area determined by the combination of FS/SS role, cover settings, and rush/pass defense call.  CBs in rush defense will be active closer to the line while in pass defense will be active based on WR distributions.  LBs that are not set to line defense will be similar to CBs only follow RB/TE distributions. (more on all of this later) 
  • Line Blocking - used at Very Short and Short locations.
    
    • Offensive players set to blocking will be involved at the line as follows:
      • LINE IN - blocking on inside line
      • LINE OUT - blocking on outside line (Tackles and out wide)
      • LINE IN/OUT - will block based on play call - inside or outside
    • Defensive players set to blocking will be involved at the line as follows:
      • LINE IN - blocking on inside line
      • LINE OUT - blocking on outside line
      • LINE IN/OUT - will be split between inside and outside line with chance to follow the ball based on play reaction.
• Calculate match ups for blocking at location.
• Determine results of blocking.
  • Based on the match up, there is a weighted result table that determines the result of the blocking.  It is limited in results based on advantage level as well as weighted in favor of the offense or defense based on how many players on each side are involved in the blocking.  These result tables are factored differently for each location so they can be adjusted independently.  The possibly blocking results are:
    • Defense Breakthrough - defense breaks through or is not affected by offensive blocking.
    • Defense Strong - defense generally wins the blocking battle.
    • Equal Blocking - at a stale mate.
    • Offense Strong - offense generally wins the blocking battle.
    • Offense Push - offense is easily handling the defensive players
• Determine players involved in the tackle attempt and calculate match up.
  • Based on the players involved in the location from the above step, select one (or more) players to actually attempt the tackle.
  • Players chosen can be weighted for selection based on position, play role (line, cover, etc) and relative ratings.
  • more than one player can make the attempt based on blocking results and number of player involved.
• Determine results of tackle attempt.
  • This is the chance the defensive players get their hands on the ball carrier, or in other words the ball carriers ability to avoid the tackle.  This would also be where a mistackle would be represented.
  • Based on the tackle avoidance match up of the players involved in the tackle attempt, as well as number of players involved, we set one of these results:
    • No Tackle - in cases where the defense didn't even attempt a tackle, typically related to the blocking result
    • Avoided - ball carrier evaded the tackle attempt.
    • Weak Attempt
    • Good Attempt
    • Strong Attempt
• if tackle attempt, determine players involved in tackle and calculate match up.
  • This will generally be the same players involved in the tackle attempt only looking at the tackle breaking ratings.
• Determine results of tackle.
  • Based on tackle break match up, result of the tackle attempt, and number of players involved there are weighted, and sometimes limited, chances of the following tackle break result:
    • Tackle Broken
    • Weak Tackle
    • Good Tackle
    • Strong Tackle
• Determine results of step.
  • If tackled, determine yardage and play is dead.
    • Yardage is determined by the location in which the ball carrier was tackled as well as the tackle avoidance result and the tackle break result.
  • If not tackled, check to see if player gets into end zone.  If so, TD and play is dead.  Otherwise, move ball to next location and move to next step.

Other checks made during this are:

• Fumbles - with a tackle, there is a check to see if the ball carrier fumbles the ball.  This is a chance based on the ball carries fumble rating (mix of a couple GD ratings) and the tackle results, as well as looking at the tackler's ratings.  A stronger tackle will increase the chance of a fumble.
• Injuries (not in yet) - when injuries are added, we can look at the various blocking results and tackle results to get a better selection for injury candidates.  The strength of tackle and player durability ratings will play a large part in this.

I may miss a few details, so if you have any questions, comments, or want more detail on something, let me know.

ANATOMY OF A PASSING PLAY
This breaks down the actions within each step of a passing play.  As the play continues, if the QB still has the ball, he will look for a target based on the playbook play settings and try to throw to that target based on different events within the play.  The defense will continue to try to get to the QB before he throws and apply pressure on him when he does throw.  Other players will be running routes or blocking on offense, and dropping back into cover or pressuring the QB on defense.

For each step, movement through each location, the following actions are taken:

• Set player involvement based on location.  This is the same as the rushing play only it looks at slightly different settings and will always calculate line players when the QB still has the ball.
• Determine line blocking results.  This is the same as rush blocking results only using slightly different formulation of ratings involved in pass blocking versus rush blocking (i.e pass blocking is more BLK and rush blocking is more STR)
  • We will determine blocking results for both inside and outside the line which is different than how we handle rushing plays.
• Determine pressure results on QB.
  • This is determined by current block results as well as the previous amount of pressure.
  • Pressure results are:
    • No Pressure - offense holding off defense
    • Light Pressure - defense getting some traction against offense
    • Moderate Pressure - QB will start to feel the pressure here
    • Heavy Pressure - defense is getting to QB
• Determine chance of a sack attempt.
  • Based on current pressure.  If defense can get to QB and attempt a sack, select defender(s) involved in the attempt.  Similar selection process as a tackle attempt.
• Select target.
  • Determine the target location for this step based on play settings and then select a player as the target based on formation distribution settings.
  • Determine exact yard line for target within the targeted location.
  • Determine defenders covering the target based on earlier player involvement values and calculate cover match up.
    • Match up ratings are different based on location of target.
  • Set cover result based on match up.  Result values are:
    • Well Defended
    • Moderately Defended
    • Open
    • Wide Open
• Determine results if defense can make a sack attempt.
  • QB can attempt to avoid the sack similar to the tackle attempt in the rush play.
  • If not avoided, QB can attempt to break the sack similar to breaking a tackle in the rush play.
  • If the QB is pressured or a sack is imminent, the QB has a chance to get the pass away to the target based on how open the target is, how pressured the QB is, and the QB's reaction rating.
  • There is also a chance that the QB throws the ball away in a similar manner.
  • If the QB is getting pressured, this is where the decision to scramble is made based on the pressure and QB ratings.
    • If QB does scramble, then the play continues using the rush steps listed above using some adjustments considering it is a scramble instead of a rush.
• If there is not play decision made based on a sack attempt or pressure, then we will determine if the QB throws the ball to the target.
  • Chance to get the ball off to the target is based on pressure, cover results, and the QB reaction rating.  Will also consider the current step as the longer the play lasts, the more likely the QB will attempt the pass.
• If the pass is thrown:
  • Determine how well it is thrown on target based on target location and pressure. results are:
    • Off target - no chance of catching the ball
    • Stretch - player will have to make a great catch to bring in the ball. Based on player's HND and ATH.
    • Slightly Off - catchable, but doesn't allow the target to get a good start to the run.
    • On Target - basically about as good as the ball can be thrown
  • Determine chance that the pass is defended.
    • This is based on how well the ball is thrown, the target location, and the ratings of the cover players.
    • It will either result in the pass being defended or not.
    • If defended it cannot be caught.
  • Determine chance of catch.
    • This is based on how well the ball is thrown and the receiver's ratings.
    • If the ball is not caught, but was thrown Slightly Off or On Target, then it is considered a drop ball.
  • If pass was defended, check chance of interception.
    • This is based on the target location, the QBs placement rating, and the defender's ratings.
    • If intercepted, check on if immediately downed or if there is a return.
• If ball is caught by receiver:
  • Determine chance that player is immediately downed based on throw result and cover.
  • If not immediately down, process run after the catch as rushing play with adjustments based on being a run after the catch.