Building Games with Gemini 3 Flash: The Agentic Leap

The End of "Wait and See" Coding

For years, using AI to code felt like a slow-motion conversation. You’d send a prompt, wait for a block of code, and then manually wire it into your project. It was helpful, sure, but the back-and-forth was often as exhausting as writing the code yourself. The developer stayed the middleman, responsible for every import and every bug fix.

With the launch of Midnight Blackjack, we didn't just use a chatbot to help us. We deployed an autonomous agent. By combining Antigravity with the raw speed of Gemini 3 Flash, we bypassed the friction and went straight to the fun part: creating a world. This is the story of how 20,000 lines of intent became a live product in just under 48 hours.

What It Means to Build "Agentically"

An AI model alone is like a smart person without hands. An agent, however, can act. During the development of our premium Blackjack game, Antigravity wasn't just suggesting code—it was performing operations.

Because Antigravity has a direct line to our terminal and filesystem, it didn't just give us a Deck class. It understood where that class should live within our existing game engine. It identified that we needed a sub-project, initialized it using Vite, and even managed the CSS transitions across multiple files without us ever having to hit "copy" or "paste."

• Real Context: Antigravity scanned our site architecture to find the perfect integration point.
• Autonomous Refactoring: It decided to switch our state management to a dynamic queue system mid-build to better handle complex split logic.
• Visual Coordination: Using Gemini 3 Flash's multimodal capabilities, the agent generated assets and thumbnails that perfectly matched our "Midnight" aesthetic.

Why Gemini 3 Flash is a Game-Dev Powerhouse

Speed isn't just a technical spec; it's a creative requirement. When we're building a game, we need to "feel" the animations. If tweaking a card-flip takes three minutes to regenerate and test, the creative spark dies.

Gemini 3 Flash operates in what we call the "Flow Zone." Its sub-second response times meant we could try dozens of different "feels" for our card dealing animation in minutes. We told the agent to "make it feel heavier," "add a subtle bounce," or "dim the table lights," and the changes appeared in the browser almost as fast as we could think of them.

But it wasn't just about speed. With a context window that can handle over a million tokens, Gemini 3 Flash never "lost the plot." It remembered a custom sound rule we set three hours ago while we were still deep in the weeds of state management.

Under the Hood: Solving the Recursive Split

The toughest part of any Blackjack game is "The Split." It turns a simple turn into a branching tree of cards, bets, and logic. If you split a pair of 8s, and then get another 8, the logic can get messy fast.

Instead of hardcoding two hands, Antigravity used the reasoning power of Gemini 3 Flash to propose a dynamic hand queue. This means the game can handle theoretically infinite splits with perfect stability. The agent handled the pointer logic and state transitions, allowing us to focus on making the sound of the chips feel just right.

// The agent designed this to handle unlimited splitting 
// without losing track of current active bets.
public async handlePlayerAction(action: 'hit' | 'stand' | 'double' | 'split') {
    const currentHand = this.hands[this.currentHandIndex];
    
    switch(action) {
        case 'split':
            if (this.canSplit(currentHand)) {
                // Agent-derived sequence for sound/UI sync
                this.performSplit(currentHand); 
                await this.sound.play('chip_bet');
                this.triggerUIUpdate();
            }
            break;
    }
}

Crafting the "Midnight" Aesthetic

We wanted our players to feel like they were sitting in a high-stakes lounge in Monte Carlo at 2 AM. This meant we needed depth, texture, and light—not just flat colors.

By describing the vibe as "moonlight reflecting off emerald felt," the agent generated a complex glassmorphism design system. We used frosted glass effects for the UI panels and radial gradients for the table, creating a faux-3D vignette that makes the game feel premium and immersive.

A Greener Way to Code

We're committed to the principles in Google's AI Playbook for Sustainability. Traditional development is wasteful—countless hours spent on redundant searches and inefficient build cycles. By using a highly-optimized stack like Antigravity and Gemini 3 Flash, we're building software more sustainably. We're reducing the total compute cycles needed to move from an idea to a finished product, proving that fast development can also be responsible development.

The Future of Creation

Midnight Blackjack is more than a game; it's a proof of concept. It shows that the gap between raw imagination and a live URL is shrinking. As these agents become more skilled and our models become even more responsive, the only limit will be our own creativity.

We're already planning our next ten projects. With this new agentic workflow, we're just getting started.