Anders Behring Breivik knew it would take practice to be able to slaughter dozens of people before being shot by police.
In a chilling summary, the far-right fanatic claimed that he sharpened his aim by playing computer games for more than a year before Norway's worst peacetime massacre.
Breivik told an Oslo court he took steroids to build physical strength and meditated to "de-emotionalise" himself before the bombing and shooting rampage that left 77 people dead.
His lack of remorse and matter-of-fact description of weapons and tactics - he even considered using a flame thrower - was deeply disturbing to families of the victims, most of whom were teenagers.
"They perceive him as evil and dangerous and reopening wounds," said Mette Yvonne Larsen, a lawyer representing the bereaved. Some of them are following the proceedings in court, others are watching it by live video-link in more than a dozen courtrooms around Norway.
Norway has been captivated by the trial since it began on Monday. The public TV network NRK is broadcasting live from the court, but is not allowed to show Breivik's evidence.
Breivik, who styles himself as a modern-day crusader, has confessed to the attacks but rejects criminal guilt, saying he was acting to protect Norway and Europe by targeting a left-leaning political party he claims has betrayed the country by opening it up to immigration.
Since Breivik has admitted to the bombing in Oslo that killed eight people and the shooting massacre at the Labour Party youth camp that left 69 dead, the key issue of the trial is to establish whether he is criminally insane.
He said he was disappointed to hear on a car radio as he was driving to the youth camp on Utoya island that the building did not collapse. He added that his original plans were to set off three bombs in Oslo, including at the royal palace, but building just one fertiliser bomb turned out to be "much more difficult than I thought".
Breivik said he had expected to be confronted by armed police when he left Oslo for Utoya island, armed with a handgun and a rifle - both named after Norse gods. "I estimated the chances of survival as less than 5%," he said.