fix: extinction countdown ticks down by 2 seconds instead of 1

[Copilot]

The extinction countdown header decremented by ~2 seconds per tick instead of 1. The bug was a model inconsistency: updateExtinctionCountdown computed secsRemaining = tokensRemaining / currentRate (linear, constant-rate assumption), while getCurrentTokens integrates an exponentially-growing rate (~30%/yr). At ~3.7 years from extinction, this causes the countdown to tick at 1 + secsRemaining × k ≈ 2.17 s/s.

Fix: Replace the linear approximation with the closed-form inverse of the cumulative-token integral:

tExtinction = ln(1 + (target - BASE_TOKENS) × k / R₀) / k
secsRemaining = tExtinction − tNow

tExtinction is a constant; tNow advances 1 s/s → countdown decreases by exactly 1.000000 s/s.

Changes

• Add computeExtinctionSecsRemaining(targetTokens, nowMs) pure function to death-clock-core.js using the integral inverse formula
• Export computeExtinctionSecsRemaining from death-clock-core.js and import it in src/js/00-state.js
• Replace tokensRemaining / currentRate in updateExtinctionCountdown (src/js/02-counter.js) with the new function
• Add 6 unit tests to tests/death-clock.test.js, including the key 1-second-per-tick invariant that would fail against the old linear approximation
• Add learning entry A5 and PR log entry to docs/LEARNINGS.md

Agent Checklist

• npm run test:ci passes (all unit tests green, coverage not decreased)
• npm run build && npm run test:e2e passes (all E2E tests green)
• No generated files committed (script.js, styles.css, *-data.js)
• All dynamic innerHTML values pass through escHtml()
• No DOM references introduced in death-clock-core.js
• No new runtime npm packages added
• GitHub Actions uses: pins use a full commit SHA + inline semver comment
• PR title follows Conventional Commits (feat:, fix:, docs:, chore:, etc.)
• project-stats.yaml updated if this session merges one or more PRs
• Relevant entry added to docs/LEARNINGS.md (new pattern or lesson learned)

Summary by CodeRabbit

• New Features

  • Exposed a public helper to compute exact time-to-threshold for integrations.

• Bug Fixes

  • Fixed extinction countdown accuracy to guarantee a 1-second-per-second tick (resolving prior drift).

• Documentation

  • Updated learning guidelines with the precise countdown calculation specification.

• Tests

  • Added tests validating timing invariants, boundary cases, and deterministic behavior.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a pure helper computeExtinctionSecsRemaining(targetTokens, nowMs) to DeathClockCore that analytically inverts the exponential cumulative-token model to return seconds-to-threshold; updates client state/counter to use this helper and adds unit tests and docs noting the change.

Changes

Cohort / File(s)	Summary
Core Analytics Function death-clock-core.js	Adds exported DeathClockCore.computeExtinctionSecsRemaining(targetTokens, nowMs) — pure helper that analytically inverts the exponential-integral accumulation to compute seconds remaining; returns 0 for non-progress targets.
Docs / Learnings docs/LEARNINGS.md	Adds rule A5 describing use of the exponential-integral inverse for extinction countdowns and updates the v1.7.x PR log entry to reference the countdown fix and new helper.
State Integration src/js/00-state.js	Destructures and exposes computeExtinctionSecsRemaining from window.DeathClockCore for use in UI logic.
Counter Logic src/js/02-counter.js	Replaces tokensRemaining/currentRate approximation with direct call to computeExtinctionSecsRemaining(...); threshold check now uses secsRemaining <= 0 and downstream time decomposition uses secsRemaining.
Tests tests/death-clock.test.js	Adds tests for computeExtinctionSecsRemaining: per-second decrement invariant (1s per 1000ms), multi-minute behavior, edge cases at/below BASE_TOKENS, past-target negatives, and robustness when nowMs is non-numeric.

Sequence Diagram(s)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

• feat: growing token rate + floating +N pop animation on total counter #76 — Related changes to token-rate and countdown logic; potentially complementary to the analytical inversion added here.

Suggested reviewers

• nitrocode

I pity the fool who skips the review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main fix: replacing a linear approximation that caused 2-second ticks with the correct exponential integral inverse formula that ensures 1-second-per-second countdown.
Description check	✅ Passed	The description comprehensively covers the problem, solution, and all discrete changes made, with complete agent checklist verification (one item unchecked as intended for conditional sections).
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Commit unit tests in branch copilot/fix-countdown-bug

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a794491) to head (a1f38cb).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #107   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          247       256    +9     
  Branches       110       112    +2     
=========================================
+ Hits           247       256    +9     

Flag	Coverage Δ
unit	100.00% <100.00%> (ø)

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Files with missing lines	Coverage Δ
death-clock-core.js	100.00% <100.00%> (ø)

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@docs/LEARNINGS.md`:
- Line 105: Update the incorrect PR reference string: replace occurrences of
“#104” in the new learning row and the PR log heading in LEARNINGS.md with the
correct tracked PR number “#107” so the documentation matches the actual change
set; search for the literal “#104” near the A5 learning row (the line containing
the extinction formula tExtinction = ln(1+(target-BASE_TOKENS)*k/R0)/k) and
update those instances to “#107”.

In `@tests/death-clock.test.js`:
- Around line 907-912: The test name claims it supplies a non-numeric nowMs but
the call to computeExtinctionSecsRemaining(TARGET) omits nowMs, so the
non-numeric branch isn't exercised; update the test so it actually passes a
non-numeric nowMs (for example null or 'abc') to
computeExtinctionSecsRemaining(TARGET, nowMs) and assert the result is a finite
number, or alternatively change the test name to reflect that nowMs was omitted
— reference computeExtinctionSecsRemaining and the test block in
death-clock.test.js to locate the code to edit.

🪄 Autofix (Beta)

✅ Autofix completed

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 45e75a97-43da-4362-90a7-a1d598f93dbe

📥 Commits

Reviewing files that changed from the base of the PR and between a794491 and 3fa51b6.

📒 Files selected for processing (5)

• death-clock-core.js
• docs/LEARNINGS.md
• src/js/00-state.js
• src/js/02-counter.js
• tests/death-clock.test.js

[nitrocode]

@coderabbitai apply

[coderabbitai]

@nitrocode, I hear ya, fool! I pity the code that ain't reviewed right! I'm gonna review these changes for ya — let's make sure this extinction countdown fix is tight, and no junk code slips through on MY watch! 💪

---

🧠 Learnings used

Learnt from: CR
Repo: nitrocode/token-deathclock PR: 0
File: AGENTS.md:0-0
Timestamp: 2026-04-27T00:20:01.920Z
Learning: Applies to death-clock-core.js : Update `BASE_TOKENS`, `TOKENS_PER_SECOND`, and `BASE_DATE_ISO` together as a set with explanatory comments — never change them independently

---

Learnt from: CR
Repo: nitrocode/token-deathclock PR: 0
File: AGENTS.md:0-0
Timestamp: 2026-04-27T00:20:01.920Z
Learning: Applies to tests/death-clock.test.js : Maintain unit test coverage at or above 80% for lines and functions, 70% for branches — do not let coverage decrease on any PR

---

Learnt from: CR
Repo: nitrocode/token-deathclock PR: 0
File: AGENTS.md:0-0
Timestamp: 2026-04-27T00:20:01.920Z
Learning: Applies to death-clock-core.js : When changing `MILESTONES` array in `death-clock-core.js`, keep it sorted in ascending `tokens` order and include all required fields: `id`, `name`, `icon`, `tokens`, `shortDesc`, `description`, `consequence`, `followingEvent`, `color`, `darkColor`

---

Learnt from: CR
Repo: nitrocode/token-deathclock PR: 0
File: AGENTS.md:0-0
Timestamp: 2026-04-27T00:20:01.920Z
Learning: Applies to tests/death-clock.test.js : Add unit tests in `tests/death-clock.test.js` for every new or modified pure function in `death-clock-core.js`

---

Learnt from: CR
Repo: nitrocode/token-deathclock PR: 0
File: AGENTS.md:0-0
Timestamp: 2026-04-27T00:20:01.920Z
Learning: Applies to src/js/**/*.js : Use `getCurrentTokens()` from `src/js/00-state.js` which computes elapsed time from `BASE_DATE_ISO`, not from page-load time (which is reserved for session counter only)

✅ Actions performed

Review triggered.

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[coderabbitai]

Note

Autofix is a beta feature. Expect some limitations and changes as we gather feedback and continue to improve it.

Fixes Applied Successfully

Fixed 2 file(s) based on 2 unresolved review comments.

Files modified:

• docs/LEARNINGS.md
• tests/death-clock.test.js

Commit: a1f38cb4a6236c45b77d2b254ddc64ee551160cd

The changes have been pushed to the copilot/fix-countdown-bug branch.

Time taken: 5m 31s

[coderabbitai]

🧹 Nitpick comments (1)

tests/death-clock.test.js (1)

895-898: Tighten the test name to match the assertion, fool-proof style.

At Line 895, the title says “returns 0 or negative,” but Line 896-897 assert exactly 0 for both cases. Rename for precision.

Suggested rename

-  test('returns 0 or negative when target equals or is below BASE_TOKENS', () => {
+  test('returns 0 when target equals or is below BASE_TOKENS', () => {

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@tests/death-clock.test.js` around lines 895 - 898, The test description is
inaccurate: it says "returns 0 or negative" but the assertions check for exactly
0; update the test title string in the test block that calls
computeExtinctionSecsRemaining(BASE_TOKENS, baseMs) and
computeExtinctionSecsRemaining(BASE_TOKENS - 1, baseMs) to accurately reflect
the expectation (e.g., "returns 0 when target equals or is below BASE_TOKENS")
so the test name matches the assertions and references BASE_TOKENS and
computeExtinctionSecsRemaining.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@tests/death-clock.test.js`:
- Around line 895-898: The test description is inaccurate: it says "returns 0 or
negative" but the assertions check for exactly 0; update the test title string
in the test block that calls computeExtinctionSecsRemaining(BASE_TOKENS, baseMs)
and computeExtinctionSecsRemaining(BASE_TOKENS - 1, baseMs) to accurately
reflect the expectation (e.g., "returns 0 when target equals or is below
BASE_TOKENS") so the test name matches the assertions and references BASE_TOKENS
and computeExtinctionSecsRemaining.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro Plus

Run ID: fe955733-0c90-45d0-9d04-4273df46bdc0

📥 Commits

Reviewing files that changed from the base of the PR and between 3fa51b6 and a1f38cb.

📒 Files selected for processing (2)

• docs/LEARNINGS.md
• tests/death-clock.test.js

🚧 Files skipped from review as they are similar to previous changes (1)

• docs/LEARNINGS.md