The chain
$1.216 for the whole chain, at each model’s list price:
- Key art: $0.053 ($0.053 per image)
- Video loop: $1.00 ($0.20 per second)
- Menu music loop: $0.16 ($0.0025 per second)
- Confirm sound: $0.003 ($0.002 per second)
summer api estimate <model> --input '<json>', or POST /v1/estimate with the same body as the job. Prices come from GET /v1/models and change only when the provider’s price does.
Before you start
Sign in once, so your agent or your terminal can run jobs on your Summer account:Step 1: key art made for a title screen
Title screen key art is not a poster. Half of it will be covered by a logo and a menu, so plan the empty spaces first.- Leave calm areas, and say where. “The upper middle is calm soft sky with little detail, for a logo. The lower left is darker and calm, for menu buttons.” Busy detail behind text makes both hard to read.
- Put the light away from the menu. The lantern sits in the right third; the menu sits in the darker lower left. White buttons read on dark, quiet ground.
- Pick things that can move forever. Fog, flame, fireflies, water, leaves, clouds, grass. These are the motions that loop. A character in a pose that must change, or a door, does not.
- No text, no logo, no letters. The logo is a separate layer, so you can change it, translate it and animate it.
- High contrast. Video models drift toward grey. Start with deep shadows and a bright light, and there is room to lose a little.
width and height ask for a picture at least 1920 by 1080, so it holds up full screen. Set aspectRatio to the screen the menu fills: 16:9 for desktop and TV. For a phone in portrait, make a second key art at 9:16: the clip follows the shape of its picture.
store-art skill lists every store slot.
Step 2: a short loop with no visible seam
Send the key art’sfileUrl as imageUrl: the picture becomes the first frame. Luma Ray 3.2 is the model for this step. It is made for cinematic camera work and silent background loops for menus, at $0.20 per second.
Video jobs on the Summer API take one picture, the first frame. There is no end-frame field, so you cannot pin the last frame to the first. You win the loop three ways instead: in the prompt, in the choice of motion, and with one short ffmpeg command after.
In the prompt. Ambient motion only. Words that loop: drift, flicker, float, blink, ripple, sway, pulse, glow, shimmer. Words that do not: walks, enters, opens, appears, transforms, falls. Add “the camera stays locked off”, “constant lighting” and “nothing enters or leaves the frame”. Put the opposite in negativePrompt: camera movement, zoom, people, lighting change, fade to black.
Short is better. Five seconds is enough. The longer a clip runs, the further it drifts from the first frame, and the harder the seam.
running, and you read GET /v1/jobs/{id} until state is done (jobs).
Play it on repeat and watch only the moment it restarts. If you see a jump, fix it with one of these. Both drop the sound track (-an): a title loop plays muted.
A crossfade loop, for fire, fog, water and particles. It blends the last second into the first, so the clip ends exactly where it begins. For a 5 second clip, offset is 3 (the length minus 2):
negativePrompt.
Other models for this step. Veo 3.1 Lite makes cheap ambient loop drafts for menus and loading screens ($0.05 per second). MiniMax H3 Max Turbo is the low-cost way to try many takes ($0.026 per second). Kling 3.0 Standard is the default video model, with fluid motion ($0.14 per second). Vidu Q4 gives smooth, steady motion from one frame, good for idle loops. Draft three takes on a cheap model, then run the best prompt on the final one.
Step 3: menu music that loops without a gap
A menu track loops for as long as the player sits there. Two things make it loop well: music written to loop, and a length that is a whole number of bars.- Ask for a loop in words. “No intro build, no fade-in, no fade-out, no ending, the last bar leads straight back into the first.”
- Fix the tempo and the meter. “90 bpm, 4/4, steady tempo, one key throughout.” A track that speeds up or changes key cannot loop.
- Pick the length in bars. One bar of 4/4 is 240 divided by the tempo, in seconds. At 90 bpm a bar is 2.67 seconds, so 64 seconds is exactly 24 bars. A loop point on a bar line is a loop point the ear accepts.
- Instrumental, calm, not too busy. The player reads menus over it. Save the big theme for the trailer.
music-track skill has more prompts for menu, level and boss music.
Step 4: a confirm sound
The first sound the player makes in your game is pressing Start. Give it a short, clean sound that fits the music: soft and warm for a cozy game, a heavy hit for an action game.loop: true and about 20 seconds. The sound-effect skill covers UI sounds and ambience.
Put it in your game
Summer Engine. Import the clip by itsassetId or from its fileUrl. Summer Engine plays video as Ogg Theora (.ogv), and the import converts the MP4 for you: load the .ogv path the import answer names. If you made a seamless or ping-pong file with ffmpeg, import that file the same way.
Build the scene in layers, back to front: the key art as a TextureRect (it shows while the video starts), the VideoStreamPlayer filling the screen, the logo, then the menu. Later children draw on top.
BackgroundLoop anchors to full rect so it fills any window. The animated-loop skill makes and wires the loop for you inside a project, and ui-graphics makes the buttons and panels in your style.
Any other engine. Play the MP4 in a full-screen video player set to loop and mute, under your UI layer. On a web page, use <video autoplay loop muted playsinline>. Loop the Ogg music on its own audio player.
Keep it light. A five-second ambient loop compresses well. Export it at 720p for mobile and web builds, and keep the key art as a still fallback for low-end devices.
Make one for every season
Once the title screen works, the chain is a template. A winter version, a Halloween version or a version per update is the same four jobs with a new key art prompt and the same loop and music prompts. Send the key arts as one batch, check them, then the loops as another:Common problems
Questions
Can I animate my own key art? Yes. Upload it (send a picture) and start at step 2 with itsfileUrl. Make sure it has the calm areas for the logo and menu.
Can the loop be longer than five seconds? Yes: you can ask for up to 20 seconds, and each model renders its nearest supported length. But a longer clip drifts further from its first frame and the seam is harder to hide. Five seconds with a crossfade looks the same to a player and costs less.
Can I use all of it in a commercial game? Yes. Every model on the Summer API allows commercial use of what it makes.
Do I need a plan? No. Jobs are paid from your paid Summer credits, your plan’s credits or a top-up. Each connected agent has its own spend limit in Settings > Connected apps.
