Guide

Game ground pound and dive stomp systems explained

Harbor Caverns' crystal gallery drops three floors into a flooded grotto: players leap from a narrow ledge, slam down on a brittle quartz plate to shatter it, then ride the debris into the lower chamber. The first build let stomp trigger from a standing jump with only half a meter of airtime, applied a flat circular damage radius regardless of approach speed, and still ran fall damage on the same frame as impact. Telemetry logged 62% failed breaks (weak points missed, floors intact) and 19% accidental self-damage deaths on the descent. After a refactor built around minimum fall-height gating, a committed-impact state with brief i-frames, velocity-scaled shockwave radius, and designer-tagged crystal weak points, break success rose to 88% and stomp-related deaths fell to 4%.

Ground pound (dive stomp, ground slam, plunge attack) is an aerial-to-ground verb: the player commits downward while airborne, accelerates into a fast fall, and delivers a high-impact landing that may damage enemies, break environment pieces, or trigger switches. It differs from bounce pads (environment launches the player up) and from passive fall damage (punishment without player intent). Stomps reward vertical reads, timing, and spatial awareness. This guide covers activation state machines, fall-speed curves, shockwave and weak-point models, combat integration, level authoring, the Harbor Caverns refactor, a technique decision table, pitfalls, and a checklist.

What ground pound is (and is not)

A ground pound converts airborne momentum into a deliberate downward strike. The verb is commit and slam — unlike double jump (upward impulse) or air dash (horizontal burst). Stomps typically require the player to be off the ground, press a dedicated input (or hold down on stick while airborne), and accept a brief recovery window on landing. Design questions: how much height is required, what breaks, who takes damage, and whether the move cancels fall damage.

Stomp archetypes

Vertical plunger — locks horizontal drift, spikes downward velocity, impact at feet only. Classic platformer stomp (Super Mario Odyssey, Celeste assist variants).
Radial shockwave — impact spawns expanding circle that damages enemies and breaks tagged tiles in radius. Action-adventure and Metroidvania staples.
Targeted dive — homing or aim-assisted plunge toward marked weak points or enemies; reads closer to an aerial melee finisher.
Charged slam — hold input in air to widen radius or increase break tier; release to commit. Rewards setup time over snap reactions.

Activation state machine

Stomp feel lives in the FSM between “player pressed down” and “impact resolved.” A minimal pipeline:

Airborne gate — reject stomp if feet contact ground (with optional coyote stomp: allow within ~80 ms of leaving ledge, mirroring coyote jump).
Minimum height — require peak altitude or fall distance above a threshold (often 1.5–3 m in platformers) so tap-stomps from hop jumps do not trigger. Harbor used 2.2 m; below that, input routes to fast-fall only.
Commit phase — lock or dampen horizontal control, apply downward acceleration curve (not instant teleport). Sell weight with pose and VFX trail.
Impact frame — raycast or overlap at feet; resolve breakables, damage, camera shake, and hitstop on successful slam.
Recovery — brief squat animation, movement lock 200–400 ms, then return to locomotion. Prevents stomp-spam on every hop.

Buffer stomp input during jump ascent (100–150 ms) so players need not frame-perfect press down at apex. Log rejected stomps (too low, not airborne) during playtest; high rejection rates mean telegraph or tutorial gap.

Fall speed, shockwaves and weak points

Impact potency should correlate with approach energy. Common models:

Velocity-scaled radius — shockwave radius = base + k × impact speed. Harbor's flat 2 m circle missed offset weak points; scaling to 3.4 m at max fall speed fixed edge hits.
Tiered break tags — brittle crystal = tier 1, reinforced stone = tier 2 (needs charged slam or item upgrade). Prevents one verb from trivializing entire dungeon.
Weak-point colliders — separate mesh child with stomp-only layer mask; center mass of floor plate, not full slab bounds. Artists mark with decal; QA verifies from player camera angle.
Enemy head-stomp vs shockwave — Mario-style top collision kills one target; radial wave hits groups. Pick one primary identity per game to avoid overlapping with melee AoE.

Fall damage policy: either grant i-frames for the committed stomp window (Harbor choice) or scale stomp damage separately from environmental fall damage. Mixing both on one frame feels like a bug.

Combat and feedback integration

When stomp doubles as an attack, wire it through the same damage pipeline as melee: team filters, invulnerability windows, and knockback direction (always downward/outward from impact normal). Strong feedback stack:

Screen shake scaled to impact tier (subtle for tier-1 crystal, heavy for boss stagger).
Particle burst at contact point plus debris spawn for breakables.
Distinct SFX layer for “whiff” (hard ground) vs “break” (crystalline shatter).
Controller rumble pulse on impact frame for gamepad players.

Offensive stomps need whiff risk: recovery squat leaves player open. Defensive stomps (escape from air combo) trade invulnerability for long landing lag — tune per genre (fighters vs platformers).

Level authoring guidelines

Stomp-gated spaces fail when readability lags mechanics:

Light cracked textures, audible crystal stress, or NPC callout before first mandatory break.
Safe rehearsal room: low fall, obvious weak point, no hazards — before multi-floor plunge.
Fall distance always exceeds minimum activation height by at least 0.5 m margin; playtest with shortest jump path.
Lower landing zone visible from stomp ledge (camera pitch assist on commit helps).
Optional soft ground below first tutorial break so failed velocity still progresses on story difficulty.

Pair stomp breaks with downstream reward (shortcut, collectible, story beat) so the verb earns memory. One-off breaks players never reuse waste tutorial budget.

Harbor Caverns refactor (case study)

Problem cluster: (1) stomp from 0.5 m hops triggered but lacked force to break tier-1 crystal; (2) flat shockwave missed weak-point offset on wide plates; (3) fall damage applied same frame as break success, killing players who correctly shattered floors; (4) no input buffer, so casual players never entered commit phase before landing.

Changes shipped:

2.2 m minimum fall-height gate with HUD ghost icon when high enough.
150 ms stomp input buffer from jump apex.
Velocity-scaled radius (2.0–3.4 m) tied to tracked peak altitude.
Committed-impact substate: 12 frames i-frames, fall damage suppressed.
Weak-point colliders shrunk to 0.6 m center discs on crystal plates.
Camera +8° pitch during commit so landing zone stays in frame.

Results: crystal-break success 62% → 88%, stomp deaths 19% → 4%, average gallery retries 4.1 → 1.3. Biggest single win was separating fall damage from committed stomp — not increasing shockwave damage.

Technique decision table

Need	Prefer	Over	Why
Break floor / switch	Ground pound	Melee smash	Aerial commit sells vertical puzzles; melee lacks height gate
Punish unplanned falls	Fall damage system	Stomp	Fall damage is passive; stomp is opt-in verb
Launch to upper platform	Bounce pad / spring	Stomp	Stomp goes down; pads own upward routing
Single-target aerial kill	Head-stomp collision	Radial shockwave	Precise top-down reads; wave is for groups
Cross wide gap downward	Stomp + break + slide	Glide only	Break enables routed descent; glide skips gate
Spam-safe traversal	Double jump / air dash	Stomp	Stomp recovery lag prevents hop-chain mobility

Common pitfalls

Stomp without height gate — hop spam triggers whiff impacts; players think input is broken.
Fall damage on same frame as break — Harbor's 19% death bucket; success feels like failure.
Flat shockwave radius — misses offset weak points on large plates.
Full-slab break collider — player aims at visual crack but physics hits edge; break fails.
Instant downward teleport — disorienting; no sell of weight or readable fall time.
Stomp during cutscene airborne — accidental sequence breaks; disable input in script volumes.
Same stomp breaks all material tiers — trivializes dungeon progression and upgrade economy.
No recovery squat — stomp becomes spammable mobility skip with no risk.

Engineer checklist

Pick archetype: vertical plunger, radial shockwave, targeted dive, or charged slam.
Implement airborne gate with optional coyote stomp window (~80 ms).
Set minimum fall-height threshold; route sub-threshold input to fast-fall only.
Add 100–150 ms stomp input buffer from jump.
Build commit phase: dampen horizontal drift, apply downward accel curve.
Scale shockwave radius or break tier from impact velocity or peak altitude.
Tag weak-point colliders on breakables; separate from visual mesh bounds.
Suppress fall damage during committed-impact i-frames if stomp is reward path.
Wire damage through combat pipeline with recovery squat and whiff vulnerability.
Author tutorial break with safe landing and visible lower chamber.
Log rejected stomps, break misses, and post-stomp deaths by room.
Playtest shortest jump path; verify margin above minimum height.
Disable stomp in scripted sequences and dialogue air states.

Key takeaways

Ground pound is an opt-in aerial verb — height gates and recovery lag define fair pacing.
Separate stomp success from fall damage — Harbor cut deaths 19% → 4% without buffing damage.
Velocity-scaled shockwaves beat flat radius for offset weak points.
Weak-point colliders must match player camera reads, not artist slab size.
Pair with bounce pads and double jump for full vertical kit; stomp owns down-break routing.