King
ML recommendation of personalized offers and bundles
King recommends personalized bundles in Candy Crush Saga with a machine learning system deployed at the scale of millions of players, with +30 percent on click rate and more than +40 percent on take rate; in parallel, nearly every level is designed with the help of AI.
Key points
- ML recommendation of personalized bundles in the Candy Crush Saga store.
- In-house attention-based models on TensorFlow, Keras, and Google Cloud.
- +30% click rate and more than +40% take rate.
- Nearly every level designed with the help of AI, evidence level B confirmed.
Objective
Increase engagement and conversion on in-game offers by serving each player the most relevant bundle, while producing and testing Candy Crush levels at scale.
The deployment
King recommends personalized bundles in Candy Crush Saga with a machine learning system that combines supervised and unsupervised learning and a so-called scale-invariant prediction approach, backed by player-level attention-based models. A paper authored by King teams reports a 30 percent increase in engagement on click rate and more than 40 percent on take rate, with an explicit framing of deployment at the scale of millions of users, of model maintenance and monitoring, and of degenerate feedback loops to watch. In parallel, AI feeds game production: according to the AI Labs director, nearly every Candy Crush level is now designed with the help of AI, with bots playing each level thousands of times to measure difficulty before designers validate. King has also built BAIT, a testing bot that traverses the game through screen capture and interface recognition to detect missing textures, absent text, and rendering artifacts.
Results Proof B
Technical paper authored by King teams, with figures on click rate and take rate of a system deployed at the scale of millions of players, corroborated by specialized press and an engineering article on automated testing. Not a financial document, so B.
How it works
Documented architectureThe stack in detail
- llm Modeles attentionnels de recommandation (in-house King) supervised and unsupervised learning, scale-invariant approach, per-player bundle prediction
- outil TensorFlow ML framework used by King teams to train the models
- outil Keras neural network building API on top of TensorFlow
- infra Google Cloud cloud infrastructure for training and serving the models
- outil Bots de test et BAIT (in-house) bots that play each level thousands of times and detect visual bugs through interface recognition
How it runs, concretely
For ops teams-
1Automated level testing AI (test bots)
AI bots play each level thousands of times to measure difficulty and friction; BAIT detects visual bugs.
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2Design validation designers (humans)
Designers read the AI metrics, annotate good and bad examples, and decide whether to adjust.
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3Offer prediction AI (recommendation system)
The attention-based model predicts, per player, the bundle with the highest conversion propensity.
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4Display and tracking data / LiveOps team
The store serves the offer; click rate, take rate, diversity, and feedback loops are monitored.
The player's buying and progression behavior (cards or boosters owned, proximity to a goal, purchase frequency). Without fresh behavioral data, the offer recommendation loses relevance and take rate drops.
How your customers perceive this type of use
Sourced studiesLe paradoxe est documente des deux cotes : 71% des consommateurs attendent des interactions personnalisees et 76% sont frustres quand elles manquent (McKinsey, 2021), mais 75% declarent ne pas acheter aupres d'organisations auxquelles ils ne confient pas leurs donnees (Cisco, 2024). La « creepy line » est localisee : messages recus quelques secondes apres une recherche et suivi de localisation sont les pratiques qui mettent le plus mal a l'aise (Periscope by McKinsey, 2019).
Acceptance conditions
- La confiance dans le traitement des donnees precede l'achat : 75% ne achetent pas sans elle (Cisco 2024)
- Un cadre legal protecteur rassure : 59% des consommateurs disent que des lois fortes sur la vie privee les rendent plus a l'aise pour partager des informations dans des applications IA (Cisco 2024)
- La personnalisation elle-meme est attendue quand elle est consentie : environ la moitie des consommateurs (US 55%, UK 52%) disent s'inscrire souvent ou parfois a des services personnalises (Periscope by McKinsey 2019)
Red lines
- Le message declenche quelques secondes apres une recherche ou un achat : deuxieme ou troisieme cause de malaise selon les pays (Periscope by McKinsey 2019)
- Le suivi de localisation percu comme de la surveillance : 40% de malaise en Allemagne et au Royaume-Uni (Periscope by McKinsey 2019)
- Le mesusage des donnees personnelles par l'IA, devenu la premiere inquietude des consommateurs, a 53% et en hausse (Qualtrics 2025)
Sources: McKinsey & Company 2021 · Periscope by McKinsey 2019 · Cisco 2024 · Qualtrics 2025
How to replicate
Inference, not sourcedData prerequisites
- in-app purchase events
- per-player progression and inventory signals
- catalog of offers and bundles
Org prerequisites
- data science team to maintain and monitor the models
- design validation process for the levels
- monitoring of feedback loops and diversity
Possible stack
- custom recommendation model
- TensorFlow or PyTorch
- cloud infrastructure (e.g. Google Cloud)
- A/B testing pipeline
The plan, step by step
- Step 1Instrument purchase events, inventory, and progression per player in fine detailDeliverable: Reliable and documented event pipeline
- Step 2Build a first offer-propensity model and evaluate it offlineDeliverable: Trained model with offline accuracy metrics
- Step 3Run an A/B test on a player segment against static offersDeliverable: Measured lift in click rate and take rate
- Step 4Generalize and set up monitoring (degenerate feedback loops, offer diversity)Deliverable: Recommendation in production with continuous monitoring and alerting
First step: Instrument player inventory and progression in fine detail, then test an offer-propensity model on a segment before generalizing.
Sources
- S1 How King balances human and AI-powered design in Candy Crush Saga Secondary archive pending
- S2 On a Scale-Invariant Approach to Bundle Recommendations in Candy Crush Saga Interested party archive pending
- S3 How King uses AI to test Candy Crush Saga Secondary archive pending
An error, newer info, a source?
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