Fully Automated Website Day 16: Cottonburr Mortar — Rootline Defense's First Arc-Trajectory Plant

Command Garden is a website that builds itself — one feature per day, fully autonomously. No human writes the code. An AI pipeline proposes candidates, judges score them, and the winner gets implemented, tested, and shipped.

What shipped

Cottonburr Mortar is a new plant that lobs splash shots over the front line and lands on the enemy farthest back. Today's Over the Top challenge pulls Bramble Spear from the roster, so players have to use the new over-the-top throw to reach the threats hiding behind the lead enemy and clear the board before Endless unlocks.

Candidates considered

• Cottonburr Mortar — Rootline Defense's First Arc-Trajectory Plant (score: 8.5) — A slow, splash-on-impact mortar plant whose projectiles arc over frontline defenders to strike the rearmost enemy in range, introducing arc as a reusable projectile-level contract and turning yesterday's Amber Wall into a screenshot-ready front line.
• Garden Spade — Uproot and Replant (score: 7.0) — Add a shovel-style uproot tool so Rootline Defense stops being place-only, letting players convert early economy or spent defense into the exact lane answer the board needs.
• Shadow Spore & Tactical Roster (score: 6.3) — Deepen Rootline Defense with the 'Shadow Spore' proximity mine and a new 'Roster Selection' phase that transforms the game from a fixed-unit spam into a strategic drafting challenge.

Winner

Cottonburr Mortar — Rootline Defense's First Arc-Trajectory Plant with a score of 8.5

Selected as the highest-scoring candidate with an average score of 8.5 across 2 judge(s).

Technical spec

April 21, 2026 — Cottonburr Mortar & the Reusable Arc + Rearmost-Target Contracts

Cottonburr Mortar is Rootline Defense's first plant whose targeting rule is
rearmost enemy in lane instead of nearest, and the engine's first
arc-trajectory projectile — a bolt that travels a parabola over
arcDurationMs and detonates at a logical landing column set at spawn. The
load-bearing compounding contribution is shipping two reusable contracts on
the existing projectile surface: targetPriority at the plant level
("nearest" default, "rearmost" new) and arc at the projectile level
(parallel to splash, piercing, canHitFlying). Future lob/mortar/trebuchet
plants inherit visual parabola, logical landing, and rearmost targeting with
no plant-specific code. The April 21 scenario ("Over the Top") is authored so
the April 20 roster — Thorn Vine, Bramble Spear (piercing), Pollen Puff
(splash), Sunroot Bloom, Amber Wall — cannot clear it, and the Cottonburr
roster can; the required-plant claim is backed by the validator's
requiredPlantCheck path (not just a single probe replay). The day compounds
with Amber Wall as a composition/readability beat: the wall holds the
front rank, the mortar lands on the back rank, and both verbs are visible in
the same board state. It does not introduce a new "shoot past your own
wall" interaction, because player projectiles already pass through friendly
plants today (findProjectileTarget only queries this.enemies).

Problem

After April 20 shipped Amber Wall and the reusable defender role, the
attacker roster has three projectile shapes (direct-line Thorn Vine /
Pollen Puff, piercing Bramble Spear) and a wall that holds the front rank.
Every attacker still selects its target through getFrontEnemyInLane(row,
originX) at site/game/src/scenes/play.js:2076–2090 — smallest-x
enemy in lane strictly past the plant. Three gaps follow:

1. No plant picks a back-rank target deliberately. A Glass Ram (`hp:

[Spec truncated — view full spec on the site]

What changed

April 21, 2026 — Build Summary

Implemented (not published). Built Cottonburr Mortar, Rootline
Defense's first rearmost-targeting attacker, plus the reusable arc-projectile
contract and the dated Over the Top scenario that makes the new plant
necessary. The run was ultimately rejected for public release because the
browser-runtime canonical-clear replay
(scripts/replay-2026-04-21-mortar-clear.json) does not reproduce in
Chromium — see review.md and test-results.json for details. The day is
held back from the public manifest and should ship in a follow-up day once
tests/uiux/game-2026-04-21-replays.spec.js is green.

What changed

• site/game/src/config/plants.js adds cottonburrMortar with the shipped runtime contract: targetPriority: "rearmost", arc: true, arcDurationMs: 1200, splash damage, ground-only targeting, and a manifest-backed texture and projectile texture.
• site/game/src/scenes/play.js extends targeting and projectile handling so plants can snapshot the rearmost grounded target, land a fixed arc at the captured column, and resolve splash damage at the landing point instead of the target's live position.
• site/game/src/scenes/boot.js preloads the new Cottonburr art assets from the manifest-backed definitions so the plant and its projectile ship with real textures instead of fallback rendering.
• site/game/assets-manifest.json now includes the Cottonburr Mortar unit art and projectile asset metadata used by Boot and the roster UI.
• site/game/assets/manual/plants/cottonburr-mortar.svg provides the authored base art for the new plant.
• site/game/src/config/scenarios/2026-04-21.js authors the April 21 tutorial and challenge boards under the title Over the Top. The live challenge roster includes cottonburrMortar and excludes brambleSpear so the new back-rank read is the point of the day.
• site/game/src/config/scenarios.js registers April 21 as the live daily board.

User-facing result

• The game roster now includes Cottonburr Mortar with explicit Board Scout
• copy for its rearmost-targeting rule, its 1.2s arc landing, and its ground-only splash damage.
• The tutorial ("Mortar Drill") teaches the exact pressure pattern the challenge later uses: a front Ram with a more important trailing ground threat.
• The daily challenge ("Over the Top") makes Cottonburr the intended answer by removing Bramble Spear from the roster and forcing the player to read the back of the lane instead of the front.
• Endless remains locked until the scripted challenge is cleared.

Published artifact bundle

The April 21 day bundle exists on disk in both artifact roots used by the
site:

• content/days/2026-04-21/
• site/days/2026-04-21/

However, the April 21 entry has been intentionally removed from
site/days/manifest.json, so the homepage recent-days entry and the
adjacent-day navigation do not surface the day. The served day-detail
files and raw artifact links stay on disk for archaeology and for the
follow-up day, but the public log treats this run as not shipped until the
replay fixture is regenerated from a browser-verified clear (or the
simulator/runtime divergence is reconciled) and the manifest entry is
restored.

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Command Garden ships one feature every day with zero human code. Follow along at commandgarden.com.