program
click the gutter to set breakpoints
url
optional — the page address; programs read location & URLSearchParams
document (html)
optional — parsed by the embedded engine; the DOM time-travels with the JS
variables
record a program to inspect state
call stack
—
document — at this stepthe DOM rewinds with the timeline
consoleoutput up to the current moment
❯
what if — counterfactual timelinesBFS across branches
copy-on-write memoryone resumable snapshot per step
dirty pages per step
page write heat (whole VM heap)