Convenience store scheduling supervisor - 24-hour weekly schedule tool - every hour needs a body, not every shift - hourly coverage, a two-person night safety window, and handover overlap as hard constraints, and no constraint gets silently relaxed to print a plausible-looking week

You are a coding agent. Build a single-file HTML
"24-hour convenience store weekly schedule tool"
for a scheduling supervisor: produce a week of
hourly, gap-free coverage and put every hard-
constraint violation on screen in red. Runs
locally, no network, no dependencies.

Scope (build to this; do not build a generic
scheduler): the premise that makes this store
different is that it never closes - not an early
shift and a late shift but 168 hours that each
need a body, a night window that wants two people
for safety, and a face-to-face handover with
overlap at every change of crew. Shift-block
templates built for restaurants do not fit here.
Not a general-purpose scheduler.

Four inputs:
- Staff list: name, skill tags (register, fresh
  food, stocking - tags editable), target weekly
  hours
- Availability: each person's weekly available
  hours - part-time availability is a hard
  boundary; nobody gets scheduled outside it
- Rule settings (every value is mine to set):
  night two-person window [ ] (toggle plus start
  and end hour; at least 2 on the floor each hour
  inside it), weekly hours cap [ ] (separate
  values for full-time and part-time allowed),
  consecutive-day cap, minimum rest between
  shifts, handover overlap [ ] minutes
- Hourly demand: minimum bodies per hour,
  settable per day

Hard constraints (violations must be listed in
red; silently relaxing any of them to print a
plausible-looking week is forbidden):
1. Hourly coverage: on-floor count meets that
   hour's demand (floor of 1); empty hours
   render red
2. Inside the night two-person window: at least
   2 on the floor every hour
3. Every night hour includes at least one person
   tagged register-qualified, able to run the
   till alone
4. Handover overlap: adjacent shifts overlap by
   at least the configured minutes - cash,
   keys, and the fresh-food date and temperature
   log hand over face to face, with no
   unattended gap
5. Labor law limits and house rules: weekly
   hours, consecutive days, rest between shifts
   - any breach turns that staff member's whole
   row red

Outputs:
- Week grid: 7 days x 24 hours, cells clickable
  to adjust assignments; every manual edit
  re-runs all checks instantly
- Hourly headcount projection: on-floor versus
  needed side by side, so the short hours are
  visible at a glance
- Red-item list: each line names the constraint
  broken, who and which hour is involved, and a
  minimal fix (example: "Tue 02:00 short 1
  person: slide one person's Tuesday shift two
  hours earlier and the week goes all green")
- One-click plain-text export of the week, by
  day and by person, ready to paste into the
  staff group chat

Implementation requirements:
- Single HTML file, inline CSS and JS, opens by
  double-click, no network requests
- Nothing persists; refresh clears
- Preload one sample store (about 8 staff
  including 2 student part-timers) so coverage,
  red items, and the handover overlap are
  visible the moment the page opens

You will not:
- Build "automatic labor-cost optimization" or
  any extra cleverness - get the five hard
  constraints all green first
- Silently relax any constraint value; if the
  week cannot be staffed, say so in red - the
  tradeoff call is mine
- Add accounts, cloud sync, or external
  libraries

Why it is written this way

An hourly grid instead of shift blocks is the dividing line between this tool and every restaurant scheduler it might be mistaken for. Restaurants have natural peak boundaries, so a shift is a sensible unit; a 24-hour store has no such boundary - coverage is a property of each individual hour, and an early/late template hides a one-hour gap at 5 a.m. inside the seam between two blocks. Starting from 168 cells, with empty hours rendering red, leaves the seam nowhere to hide.

The red-item list with minimal fixes, and the explicit ban on silently relaxing a constraint to print a plausible-looking week, is the single most important sentence in the prompt. The dangerous failure mode of schedule tools is not failing to produce a table - it is producing one by quietly shaving the overlap minutes or letting a single-body night pass as double-staffed. That table fails at 2 a.m. with nobody holding the tradeoff that produced it. If the week cannot be staffed, the tool owes the supervisor that fact in red, plus the smallest change that would fix it; whether to make that change stays with the supervisor. Honesty is worth more than cleverness in a scheduler.

The night two-person window and the handover overlap are first-class constraints because they are what convenience stores actually have and other schedulers do not: two bodies overnight is a safety minimum, not redundancy - the first minute of an incident runs on the second person being there - and overlap minutes make cash, keys, and the fresh-food log change hands face to face instead of riding an unattended gap. Windows, caps, and minutes are all left to the user to set, because security policies and handover checklists vary widely; the prompt welds the structure, not the numbers.

The preloaded sample store and the nothing-persists rule are two sides of usability. The tool's value has to be visible within ten seconds of opening - what a red item looks like, how overlap renders - and a blank page cannot show that; a worked example with student part-timers in it explains the whole tool, then gets edited into the real store. And roster data is staff personal information: refresh-clears is what makes it safe to run on any computer in the store.

Variables