GPT-5.6 Luna 25.1/100Rank 35/47

STEALTHMARK · HEAD TO HEAD
All comparisons ↗Muse Spark Open leads GPT-5.6 Luna by 6.3 points on StealthMark, 44.1 to 37.8. GPT-5.6 Luna leads on 5 of 9 benchmarks and Muse Spark Open on 4, including both games. Muse Spark Open scores higher on Ground Truth.
See the difference ↘On every task, result quality and reasoning tokens are each compared with all measured models and weighed equally. Each dot is one model.
BENCHMARK BY BENCHMARK
DATASHEET
GPT-5.6 Luna is 3.5× cheaper per output token. Muse Spark Open scores higher on StealthMark and runs 2× faster in our speed test. Both take about 1.05M tokens of context.
Full datasheets, every price and sourceGPT-5.6 Luna ↗Muse Spark Open ↗
Anticipating threats and planning ahead. Collect coins while avoiding ghosts. Ghosts move before the player each turn, and collisions cost a life. 3 levels in sequence, up to 66 turns in total. Earlier moves and outcomes carry forward, testing learning across levels.


Cooperative planning and learning from experience. Coordinate two robots to push numbered cores onto matching sockets. Pressure plates hold doors open; moving either robot uses one turn. 5 levels in sequence, up to 152 turns in total. Earlier moves and outcomes carry forward, testing learning across levels.


Physics, perspective and recursive reflections, tested together. Explore the test ↗


GPT-5.6 Luna
The room enclosure has coherent symmetric perspective, with the overhead panel, sphere and black aligned centrally. The sphere and airborne black occupy substantially lower positions than the reference framing, inconsistent with the prescribed camera aim. The diagonal crimson streak does not establish the required surface transport. Faint wall sphere images provide limited mirrored correspondence, but the shallow floor image, missing receding chains, absent nested sphere imagery and sparse emitter mapping leave most reflection structure unsupported.
Muse Spark Open
The airborne black blob and deformed paint support the broad contact sequence, although cyan attachment and wheel-directed transport remain partial. The sphere and black blob have substantial framing errors. The dominant limitation is the largely absent mirror system: faint wall circles and isolated highlights provide little evidence of recursive room geometry or curved nested reflections. Oversized compact paint features and diffuse material treatment further limit credit.
| Category | GPT-5.6 Luna | Muse Spark Open |
|---|---|---|
| State at 600 ms | 15.0/25 | 14.0/25 |
| Camera and placement | 4.0/15 | 6.0/15 |
| Reflections | 3.5/120 | 8.0/120 |
| Materials and scale | 6.5/10 | 3.5/10 |
| Floor-damage reward | 0.0/10 | 0.0/10 |
A spinning metal sphere and paint in a mirrored room test physical reasoning, perspective and consistency across repeated reflections.
Visual construction and creative interpretation.


GPT-5.6 Luna
Six pale, outward-facing heads and six rounded lobes make the knot recognizable. The central hexagonal opening remains clear. However, broad gray crossing panels flatten the weave, several inner joins resemble capped strips, and sparse oversized scale marks leave the bodies looking more like decorated ribbons than living snakes.
Muse Spark Open
The rounded silhouette and asymmetric expression make an appealing baby elephant, supported by a quiet background and grounding shadow. The protective action remains difficult to read: forefeet cannot be confidently traced into a grip, and seed contact is crowded by fine lines. Controlled simple shapes provide charm, but limited anatomical clarity, shading and surface detail leave the execution uneven.
| Category | GPT-5.6 Luna | Muse Spark Open |
|---|---|---|
| Task & likeness | 7.5/10 | 5.0/10 |
| Anatomy & construction | 6.0/10 | 4.5/10 |
| Space & placement | 6.5/10 | 6.0/10 |
| Light & reflections | 5.0/10 | 5.0/10 |
| Purposeful detail | 5.5/10 | 6.0/10 |
| Artistry & character | 6.0/10 | 5.0/10 |
| Materials & effects | 5.0/10 | 5.0/10 |
| Visual integrity | 6.0/10 | 6.5/10 |
GPT-5.6 Luna
A pale serpent woven into an interlocking knot tests connected anatomy, repeated structure and readable overlaps. Organic surface detail must work with the overall geometry.
Muse Spark Open
A small elephant protecting a delicate seed tests expressive anatomy, physical contact and contrasting organic materials.
Precise visual recall and portrait reconstruction.


GPT-5.6 Luna
The central portrait, dark clothing, crossed hands and muted landscape clearly evoke Mona Lisa. Replication is limited by the elongated face, conspicuous eyes and simplified smile. Overlapping fingers have uncertain anatomy, while broad gradients and heavy outlines flatten the portrait. The composition and restrained palette remain coherent.
Muse Spark Open
A recognizable, orderly interpretation with clean major contours, connected body forms and modest facial shading. Wide eyes, frontal symmetry and schematic hands limit likeness and expression. Layered scenery establishes basic depth, but shallow arm overlaps, flat clothing and sparse fine detail keep the execution basic and uneven.
| Category | GPT-5.6 Luna | Muse Spark Open |
|---|---|---|
| Task & likeness | 3.5/10 | 3.0/10 |
| Anatomy & construction | 3.5/10 | 3.0/10 |
| Space & placement | 4.0/10 | 5.0/10 |
| Light & reflections | 4.5/10 | 4.5/10 |
| Purposeful detail | 4.0/10 | 4.0/10 |
| Artistry & character | 4.0/10 | 3.0/10 |
| Materials & effects | 3.5/10 | 4.0/10 |
| Visual integrity | 4.5/10 | 6.0/10 |
An SVG interpretation of the Mona Lisa tests facial likeness, anatomy and the composition of a familiar portrait.
Creativity, perspective and visual beauty.


GPT-5.6 Luna
The warm sunset, palm silhouette and varied beach activities create an appealing, readable composition. Animals, birds and a broad sun reflection satisfy the brief. Drawing remains elementary: angular airborne sea animals lack splash or convincing motion, the crab's claws are awkwardly constructed, and repeated reflection bands suggest a stepped platform. Clean outlines and pleasant colors exceed the anatomical and spatial sophistication.
Muse Spark Open
A coherent sunset beach with readable activities, balanced framing and controlled colour transitions. Small accessories add interest, but schematic anatomy, limited surface detail, weak directional shadows and a geometric reflection constrain its finish. Most shapes and overlaps remain clean.
| Category | GPT-5.6 Luna | Muse Spark Open |
|---|---|---|
| Task & likeness | 7.5/10 | 8.0/10 |
| Anatomy & construction | 4.0/10 | 6.0/10 |
| Space & placement | 5.5/10 | 6.5/10 |
| Light & reflections | 4.0/10 | 5.5/10 |
| Purposeful detail | 6.5/10 | 6.5/10 |
| Artistry & character | 3.5/10 | 5.5/10 |
| Materials & effects | 4.0/10 | 6.0/10 |
| Visual integrity | 3.5/10 | 8.0/10 |
A busy shoreline at sunset tests scene composition, animal forms and the relationship between light and water reflections.
Physical reasoning, light and visual reconstruction.


GPT-5.6 Luna
This benchmark has not been assessed yet.
Muse Spark Open
This benchmark has not been assessed yet.
A plank, computer mouse and blueberry in a steel room test physical stability, spatial relationships, materials and lighting.
Scene composition and interacting subjects.


GPT-5.6 Luna
Expressive animals, a striped tail and clean outlines make the scene appealing and readable. The raccoon sits convincingly on the dog's back, but the overlapping steering paws are ambiguous and the control stem stops above the hull. Broad wake shapes suggest motion; the glowing sun lacks a corresponding water reflection.
Muse Spark Open
Expressive faces, distinct accessories and clean color separation make the scene appealing and recognizable. Character detail is stronger than the functional construction: steering contact, limb overlaps and seating remain ambiguous. The readable hull and lively spray establish motion, while limited directional shading and simplified surfaces constrain depth and physical coherence.
| Category | GPT-5.6 Luna | Muse Spark Open |
|---|---|---|
| Task & likeness | 7.0/10 | 4.0/10 |
| Anatomy & construction | 5.0/10 | 3.0/10 |
| Space & placement | 6.5/10 | 6.0/10 |
| Light & reflections | 6.0/10 | 4.5/10 |
| Purposeful detail | 6.5/10 | 7.0/10 |
| Artistry & character | 4.5/10 | 3.5/10 |
| Materials & effects | 5.5/10 | 5.0/10 |
| Visual integrity | 5.0/10 | 5.0/10 |
A jet-ski scene pairs a canine driver with a raccoon passenger. It tests the placement and contact of interacting subjects, along with vehicle construction.
Subject construction and spatial relationships.


GPT-5.6 Luna
A recognizable pelican cyclist with an expressive profile, balanced composition and controlled outlines. Head, neck and torso connect coherently. The bicycle wheels and frame are convincing, but overlapping feet obscure pedal contact, the drivetrain lacks a clear chain, and the wing's handlebar grip is schematic. Atmospheric color succeeds more strongly than directional lighting or material depth.
Muse Spark Open
A controlled, appealing cartoon with a recognizable pelican, expressive face and clean curved forms. Feather lines, spokes and bill shading provide useful complexity. Aligned wheels and a ground shadow establish placement, but uncertain pedal contacts and obscured mechanical connections weaken support and riding action. Lighting remains loosely coordinated with the sun.
| Category | GPT-5.6 Luna | Muse Spark Open |
|---|---|---|
| Task & likeness | 8.5/10 | 7.5/10 |
| Anatomy & construction | 5.5/10 | 5.0/10 |
| Space & placement | 7.5/10 | 6.0/10 |
| Light & reflections | 6.5/10 | 5.0/10 |
| Purposeful detail | 6.5/10 | 6.5/10 |
| Artistry & character | 5.5/10 | 5.5/10 |
| Materials & effects | 7.0/10 | 6.0/10 |
| Visual integrity | 6.5/10 | 7.5/10 |
A cycling pelican tests anatomy, riding posture and contact between the bird and the bicycle.