1. Performance Efficiency

Sub-characteristic	Source	Stimulus	Artifact	Environment	Response	Response measure
Time behaviour	Player	Presses “Confirm move”	Client + P2P link	1-on-1 match, stable Wi-Fi ≥ 20 Mbps	Peer sends move packet, opponent sees its animation	End-to-end latency ≤ 150 ms for 95 % of moves
Resource utilisation	Profiling system	30-minute game session	Android client	Battery 50 %, 8-core CPU, 4 GB RAM	Engine maintains average CPU load	≤ 15 % average CPU and ≤ 250 MB RSS
Capacity	1 000 players	Peak concurrent users	Signalling server	VPS 2 vCPU / 4 GB RAM	WebRTC rooms are created	≥ 400 simultaneous tables without signal-time degradation (≤ 1 s)

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2. Compatibility

Sub-characteristic	Source	Stimulus	Artifact	Environment	Response	Response measure
Interoperability	Player (Android)	Connects to a table created on Windows	Two Godot clients	Different OSs, NAT network conditions	Exchange SDP/ICE, game starts	Handshake completes ≤ 2 s, success rate ≥ 99 %
Co-existence	Operating system	Video-call app running concurrently	Game client	Mobile device with another WebRTC application	Game limits channel bit-rate	Average share of bandwidth ≤ 40 %

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3. Reliability

Sub-characteristic	Source	Stimulus	Artifact	Environment	Response	Response measure
Availability	Player	Opens lobby	Signalling server	24 × 7 operation	Returns table list	Availability ≥ 99.8 % per month
Fault tolerance	Network	10 % packet loss for 5 s	P2P link	Match in progress	Missing state frames are re-requested	Game continues without disconnect; skipped moves = 0
Recoverability	ISP	Connection drop for 30 s	Client	Mobile 4G → Wi-Fi	Client reconnects and restores the game	Full recovery ≤ 10 s, lost moves = 0

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4. Security

Sub-characteristic	Source	Stimulus	Artifact	Environment	Response	Response measure
Confidentiality	Malicious sniffer	Passively listens traffic	P2P data	Public Wi-Fi	DTLS encrypts the channel	Impossible to extract card contents (probability < 10⁻⁶)
Integrity	Man-in-the-Middle att.	Substitutes move packet	P2P link	In-transit	Client rejects packet via HMAC	100 % of attacks detected, game continues
Authenticity	Player	Logs into account	Signalling server	OAuth2 + JWT	Verifies token and issues ICE creds	Invalid tokens rejected ≤ 100 ms; false positives < 0.1 %

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5. Flexibility / Portability

Sub-characteristic	Source	Stimulus	Artifact	Environment	Response	Response measure
Adaptability	Producer	Web version required	Game repository	CI/CD, Emscripten	Build to WebAssembly	Successful build with no code changes, ≤ 2 days
Installability	New user	Clicks “Install” on Steam	Distribution	Windows 11	Client downloads and launches	Successful installation ≥ 99 %, first window ≤ 15 s
Replaceability	DevOps	Migrate signalling server to another VPS	Docker container	Zero-downtime deploy	Old traffic drained, new instance up	Match downtime = 0 s; rollback ≤ 1 click