# SSBM tech: the code

Teching in SSBM depends on two values: `timer_LR` and `since_rapid_lr`.


## How do these values behave?

Both values initialise at -1 at game start.

`timer_LR`: 
- sets to 0 on any digital trigger press.
- increments every frame unless it is equal to -1.
- naturally overflows from 127 to -128 when incrementing.

`since_rapid_lr`:
- records the exact value of timer_LR at the last digital trigger press. 
- does not increment, is not a timer.


## What this means for logic

On the frame a trigger press is recorded: 
- `since_rapid_lr` is set to the value of `timer_LR`. 
- `timer_LR` is then set to 0.


## When can I tech?

A tech happens if and only if: the player is in hitstun or tumble (aka any variant of the DamageFly or DamageFall states) && 0 <= `timer_LR` < 20 && (`since_rapid_lr` < 0 || 40 <= `since_rapid_lr`)


## What is the tech window, and what is a lockout?

tech windows and lockouts are purely conceptual:
> the `tech window` corresponds to the period of time where `timer_LR` is counting up from 0 to 20 and `since_rapid_lr` is not between 0 and 40.
>
> the `tech lockout` is simply whenever both `timer_LR` and `since_rapid_lr` are between 0 and 40, as another trigger input will keep this state going with `timer_LR` reset to 0.