With the ubiquity of the neural net, gaining access to processing centres - either an organic brain, or an artificial cortex - became orders of magnitude more straightforward. What once was a complex labyrinth of blind alleyways and educated guesswork was now accessible via a long, but comprehensible API. The efficiency of almost everything improved as more and more aspects of day-to-day life became entwined with the individual's neural net: a flexible, physical web of biocompatible fabric, painlessly installed at birth or retrofitted in adulthood. The neural net itself sits between the dura and arachnoid matter, and is often terminated in an interface near the brainstem.
Simple BTLs that stimulate reward centres, or induce hallucinations, have been in existence almost since the development of the neural net itself, using a transcutaneous interface to the neural net itself, and basic electrical stimulation via the interfacing protocols provided by the ubiquitous neural net standard. Usually translucent with a foil or colourful motif to denote the type or creator of the BTL, these proved very popular and in many cases supplanted existing recreational drugs as a cleaner, safer "escape".
In INSILICO during the first half of 2490, a series of unethical hacks by someone in a local position of higher authority, caused widespread outrage amongst the population, and the ruling corporation, AGIS, released a series of anti-hacking wetware defence tools. Available for free to everyone, the wetware, formally described by AGIS as "OpenCountermeasures", allowed the potential victim of any hack to automatically defend their data from hackers and other malfeasants a range of negative effects to choose from, with effects ranging from mild shocks, to selective cognitive dysfunction - ostensibly to lower the perpetrator's ability to perform subsequent hacks, through to coma or (in the case of select assets) death.
After the release of the OC software, successful hacking rates across the city dropped by a factor of 5 overnight as registered citizens and civilians raced to protect their most precious personal property - their data - and only the most capable of hackers stand a chance of completing a job without at least some lingering effects.
Partial schematic documentation covering some of the implementation details surrounding the breathtaking complexity of the targeted effects of the wetware was stolen from AGIS Medical in the south-western district of the city, with the perpetrators still at large. It is almost certain that a malign force has reverse engineered sections of the OpenCountermeasures' very specific neural pathway manipulation in order to optimise and unleash a new wave of enhanced BTLs, resulting in a designer, boutique experience for those able to source and afford them.
What goes up, must come down; the engineering of these BTLs is far from perfect - a mottled cousin of the AGIS technology from whence it came, and the lingering side effects of these next-generation BTLs can be severe with disruption to the alkali and alkaline earth ion channels in the brain, but to those who really need an edge, or who are looking for the ultimate escape, they remain unrivalled, and even days of side-effects will not deter them - to the extent some people will take multiple BTLs, enjoying the highests of highs, but subjecting themselves to long, drawn-out effects, leaving them vulnerable for considerable periods - and with few regrets.