Find out why Apple will reject your app before you submit
Python framework for building and simulating dynamical systems using block diagrams
Stage
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Founded
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Based in
TR
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Pricing model
Paid
Open source
Pricing
Free: 10-question metadata review with no account. One app: $12 for full 54-point scan with 3 days of unlimited re-scans. Five apps: $39 ($7.80 each) for 5 credits. Studio: $99 for 20 apps ($4.95 each). One-time payment, no subscription. All prices exclude VAT.
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Key features
54-point binary and metadata checks covering privacy, runtime, app completeness and provisioning
Each issue includes guideline number, evidence and plain-English fix
Support for Expo, Xcode, Rork, a0 and Bolt builds
Privacy-first approach with JSON-only server communication
Rejection guarantee refund if approved app marked as passing fails review
30+ solvers including implicit, explicit, and adaptive integrators
Zero-crossing detection and scheduled events for hybrid systems
Hot-swappable blocks and solvers during active simulation
Hierarchical subsystems for modular component design
MIMO support with multiple input and output ports
Browser-based visual editor with PathView
Domain toolboxes for chemical, battery, vehicle, flight, and RF engineering
Custom blocks through subclassing the base Block class
Supports continuous-time, discrete-time, and hybrid systems
FMI integration to wrap Co-Simulation and Model-Exchange FMUs
What makes it different
One-time payment per app with no subscription
Unlimited re-scans for 3 days after purchase to verify fixes
Built by an iOS developer with focus on preventing avoidable rejections
Readable, scriptable alternative to traditional simulation tools with solver depth
Full ecosystem including FastSim Rust engine and standalone C code generation
Minimal runtime dependencies: only numpy, scipy, and matplotlib
Domain-specific toolboxes for chemical, battery, vehicle, flight, and RF engineering
RejectProof