DavidCan Gemini 4 Argon build a real app, not just a pretty demo?
This guide shows how to build an app with Gemini 4 Argon in Base44, from a first prompt to logins, payments, and a live published app.
Continue reading, to find out how a six-prompt journal app called Lumen was built, tested, and upgraded to a paid product.
Gemini 4 Argon App Test
Most AI app videos stop after the first prompt, which is the easy part because the model has nothing to contradict yet.
The real test is the tenth decision, when the model must stay consistent with the previous nine.
Base44 Model Selector
Base44’s model selector sits below the prompt box and defaults to Auto, which picks a model for each request.
Click the model button and choose Gemini 4 Argon, which needs Base44’s Builder plan or higher.
You can switch models later from the bottom of the AI chat in the editor.
Liquid Glass App Design
Prompt 1 asked for Lumen, a journal app in Apple’s iOS 26 liquid glass style, with gradient backgrounds, frosted surfaces, and smooth animations.
It included a home screen with a daily entry card, an entries list by date, and an editor with a title, text, and five moods.
Tags, search, AI, accounts, and payments were deliberately left for later prompts.
Journal Tags, Search and Calendar
Prompt 2 added colored glass tag chips, favorite stars, and a search bar covering titles, content, and tags.
It also added filters for mood, tags, and favorites, a calendar that marks writing days, and a streak card for consecutive days.
Everything kept the same liquid glass design without changing how the journal originally worked.
AI Journal Reflection Features
Prompt 3 used Base44’s built-in AI integration, so no external service or API key was needed.
A Reflect button gives a short response and a follow-up question saved with the entry, plus a daily writing prompt on the home screen.
A floating assistant bubble lets users ask questions about past entries, with suggested questions, loading animations, and a retry option.
Base44 User Authentication
Prompt 4 added sign-up and login screens, so every user sees and edits only their own entries.
It also added a profile page with the user’s name, an initials avatar, and a log out button.
The app was then published, and a fresh Google account confirmed the journal started empty with no one else’s entries.
Stripe Subscription Setup
Prompt 5 created Lumen Premium, a monthly subscription handled through Stripe in test mode, so no real money is charged.
Free users see a blurred insights preview and an upgrade prompt, and subscribers get a premium badge and a manage option.
Stripe Checkout does not work in the Base44 editor preview, so you must test it on the published app.
Premium PIN Entry Locking
Premium unlocks entry locking, which protects individual entries with a four-digit PIN.
It also unlocks insights with mood trends, writing statistics, common themes, and an AI-generated monthly summary.
App UI Polish Prompt
Prompt 6 reviewed the whole design in one pass instead of fixing screens one at a time.
It made blur, highlights, shadows, and corners consistent, then added empty-state messages, loading indicators, and better mobile readability.
The instruction to keep all existing features exactly as they were helped prevent regressions.
End-to-End App Testing
The final test ran on the published app with a brand-new account: entries, tags, favorites, search, filters, calendar, and AI features.
It then checked that free accounts hit the upgrade wall, a test-card checkout unlocked premium, and the layout fit a mobile screen.
Testing the published version matters because features built across several prompts can behave differently once combined.
Gemini 4 Argon Build Takeaways
Start with the basics, then build in smaller prompts, and keep telling the model what to leave for later.
The same approach works for other app ideas, and you can read our Gemini 4 Argon tutorial for other ways to use the model.
You can also compare tools in our AI workflow app
Can Gemini 4 Argon build a full app in Base44?
Yes. In this test it built Lumen, a journal app, across six prompts, including tags, search, AI features, login, Stripe subscriptions, and a final UI polish.
How do I select Gemini 4 Argon in Base44?
Click the model button below the prompt box on the Base44 homepage and choose Gemini 4 Argon. The same selector is at the bottom of the AI chat in the editor.
Which Base44 plan do I need to choose a model manually?
Manually selecting a model requires Base44’s Builder plan or higher. On Auto, Base44 picks a model for each request.
Do I need an API key for AI features in Base44?
No. Base44 has built-in AI integration, so you can add reflections, daily prompts, and an assistant chat without an external service or API key.
Why can’t I test Stripe checkout in the Base44 preview?
Stripe Checkout does not work inside the Base44 editor preview. Publish the app and test the payment flow on the live version.
Can I test Stripe payments without charging real money?
Yes. Stripe runs in test mode, so you can complete checkout with a test card and no real money is charged.
How should I prompt an AI app builder for complex apps?
Build in layers. Start with the design and core features, then add one group of features per prompt, and tell the model what to leave for later.
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