Zombie file · Mechanical Snowfield (Outskirts)

Wheel Zombie

Most of the threat is the wheel. Separate them, and things improve.

Body durabilityvaries by difficulty, about 34–60 peas

Speednormal

Lore

Wheel Zombie pushes a stone wheel that can take about 180 peas. The wheel crushes plants, though hard plants such as Wall-nut and Enzymei can hold it back for a while.

The wheel is hard to understand. It rolls far when pushed, yet stops quickly on the ground; it seems light because it can be pushed, yet it is very tough. Once you find the motor inside, everything starts making sense.

Mechanics

Role

Pushing machine · Crushing threat

Body durability varies by difficulty, about 34–60 peas; normal speed.
The stone wheel can take about 180 peas and crushes plants.
Hard plants can temporarily block the wheel.
Power Peony's charged projectiles can push the wheel, and multiple Peonies can even make it roll back over zombies.
After the zombie is separated from the wheel, the remaining threat drops a lot.

Advanced mechanics

Wheel Zombie's advanced mechanics are two objects working together: a body that catches up and pushes, and a stone wheel with its own HP, speed, and collision resolution. The threat is the contest between body impulses, wheel kinetic energy, hard-plant absorption, and Power Peony reversal.

Body, wheel, and visible damage bands

Wheel Zombie is not a single health bar. The body maximum is about 1000, 1200, 1400, 1600, or 1800 HP depending on difficulty. The main-entry shorthand reads the work needed to push the body into its critical window, about two thirds of that maximum, and does not include the wheel.

The stone wheel is an independent machine object with 3600 maximum HP and no body-style critical reserve. Its visible damage has four bands: below 2700, 1800, and 900 HP, the wheel switches to progressively more damaged appearances. Those bands describe the wheel only, not the body.

The practical reading is layered: damage on the body ends future pushing sooner, while damage on the wheel is spent into a separate 3600 HP obstacle. A wheel that already has speed continues resolving through its own kinetic state.

\begin{aligned}H_{\text{body,max}}&\in\{1000,1200,1400,1600,1800\}\text{ HP}\\H_{\text{to critical}}&\approx\frac{2}{3}H_{\text{body,max}}\\H_{\text{wheel}}&=3600\text{ HP},\quad B_{\text{damage}}=\{2700,1800,900\}\end{aligned}

Body and wheel resolve separately: the body supplies future pushes, while the wheel carries HP, speed, and crushing collisions.

Push loop and separation window

On entry, the stone wheel appears ahead of the body and starts rolling toward the plants with initial speed. The body then catches up; when both objects align in the same lane, the position window is valid, and the wheel speed is not out of control, the body enters the pushing action.

A completed push adds about 2.0 speed units of plant-side impulse to the wheel. The wheel is also subject to ground friction, so its speed gradually returns toward zero. Hard plants absorbing kinetic energy, Power Peony reversing the wheel, excessive wheel speed, or positional offset can all break the push link.

Separation does not make the wheel safe immediately. If the wheel still has speed, it continues crushing through that speed; if the body remains alive and catches up again, it can re-enter the push loop. Stable handling usually means stopping the wheel, pressuring the body, and preparing for the next impulse at the same time.

v_{\text{wheel}}\to0\quad(\text{ground friction}),\qquad I_{\text{body push}}\approx2.0\;\text{speed units toward plants}

The body is dangerous because it can repeatedly refresh wheel speed; the separation window must be maintained through blocking, reversal, or killing the body.

Crushing and hard-plant absorption

A moving wheel reads collision targets while it has speed. Ordinary low-HP plants are usually crushed, and the wheel loses little speed from them. Hard plants use a different resolution: they convert the wheel's current kinetic energy into their own HP loss.

A useful approximation is that a hard plant absorbs the lesser of its remaining HP and 400v², after which the wheel loses the corresponding amount of speed squared. Higher speed therefore costs the hard plant more HP; if the hard plant can absorb the whole kinetic packet, the wheel stops.

This is the value of Wall-nut and Enzymei. Wall-nut has more HP and can intercept repeatedly; Enzymei has less HP, but can protect an inner same-tile plant and buy the separation window. Neither permanently disables the wheel; each converts the current speed into defensive HP loss.

D_{\text{hard plant}}=\min(H_p,400v^2),\qquad v'=\operatorname{sgn}(v)\sqrt{\max(v^2-D/400,0)}

Hard plants turn current wheel speed into HP loss; if the body can push again, the stop is only a timing window.

Electric projectile reversal

When a Power Peony electric projectile hits the stone wheel, it writes horizontal momentum into wheel speed. A normal shot applies about 0.5 impulse; a charged shot applies about 2.0, four times the normal value and large enough to contest one ordinary body push.

The impulse is not simple linear addition. It behaves closer to speed-squared composition: same-direction impulse increases wheel speed, opposite impulse cancels existing speed first, and a stronger opposite impulse reverses the wheel toward the zombie side.

A reversed wheel still uses the same collision and HP model, so it can damage zombies on the way back. Doing this reliably usually requires staggered Peonies, or a hard plant first absorbing the body's push speed before charged shots drive the wheel back.

I_{\text{normal shot}}\approx0.5,\qquad I_{\text{charged shot}}\approx2.0=4I_{\text{normal shot}}

A charged electric projectile is about four times a normal projectile's impulse; repeated reverse impulses can turn the wheel from a pusher into a counter-crusher.

Tactical reading

The answer to Wheel Zombie is not simply stacking damage. The worst board state is a wheel that still has speed, a body still able to push, and no front plant with enough HP to receive the next crush. Once body and wheel are kept apart, the threat quickly drops from a pushing machine to a manageable walking body.

Priority depends on formation. Without hard plants, pressure the body or use Peony to rewrite wheel speed. With Wall-nut or Enzymei, absorb the current speed first and then focus the body. With several Peonies available, actively look for the reverse-crush window.

Read layers separately: the body supplies impulse, while the wheel supplies crushing; do not merge their HP pools into one target.
Hard stop: Wall-nut and Enzymei convert speed into HP loss and buy time to remove the body.
Peony reversal: normal shots adjust speed, but charged shots are the reliable way to contest pushes and create counter-crushes.
Repeated pushes: stopping one roll is not enough; if the body survives and catches the wheel, the loop can restart.

Interactions & counters

Wall-nutHard plants can temporarily stop the wheel.
EnzymeiThe shell also works as a hard plant, absorbing wheel speed while protecting the same-tile inner plant.
Power PeonyCharged shots can drive the wheel; several Peonies can even push it back into zombies.