Rhythm Force

Cinevva's analyzer read this game's design doc and its source, then wrote the brief below. "Make your own" hands it to the game creator as your opening message, so you start from a real spec rather than a one-line idea.

Create a playable browser rhythm game titled “Rhythm Force,” styled as a neon cyberpunk 4-key rhythm game. Use a full-screen responsive canvas over a dark purple/black interface with Orbitron/Rajdhani-style futuristic typography, subtle scanlines, a faint perspective grid receding to a central horizon, colored lane glows, and soft neon bloom. The title screen should show a large centered gradient logo reading “RHYTHM FORCE,” with the subtitle “4-KEY RHYTHM GAME” and blinking text “PRESS ANY KEY TO START.” Any key or a title-screen tap advances to song selection.

Song selection should present two glowing glass-like cards: the built-in track “NEON CASCADE” (Built-in · 150 BPM · ~42s) and a custom-song card allowing the player to upload MP3/MP4/audio files. Include BACK and KEYBINDS buttons. The built-in song is a synthesized electronic track with kick, snare, hi-hat, bass, lead melody, and arpeggio, approximately 42 seconds long at 150 BPM. For custom audio, decode the uploaded file and generate a chart by detecting RMS/spectral-flux onset peaks, with difficulty-dependent sensitivity and density.

After selecting a song, show four difficulty cards: EASY (“For beginners,” one dot, about 2 notes/sec, normal scroll), MEDIUM (“Stepping it up,” two dots, about 3.5 notes/sec, faster scroll), HARD (“Challenge accepted,” three dots, about 6 notes/sec, still faster scroll, occasional simultaneous notes), and ASDFGHJKL (“Pure chaos. GL.”, four dots, about 10 notes/sec, very fast scroll, dense fills and chords). Selecting a difficulty shows a loading/analyzing screen with status text, percentage, and a horizontal progress bar, then begins a countdown displaying 3, 2, 1, GO! before the audio and chart start.

Gameplay is a vertical four-lane note highway centered on screen. Each lane is a narrow translucent vertical column with colored edge lines and a fading glow into the bottom. Lane colors, from left to right, are magenta/pink #C24B99, cyan #00AFFF, green #3EC94F, and hot pink/red #FF3C6B. At roughly 82% of the screen height, place four circular receptors, one per lane: idle receptors are dark hollow rings with colored outlines and a small plus/cross inside; when pressed they scale up slightly, glow, and become bright filled radial-gradient circles. Falling notes are luminous colored circular gems with white borders, radial highlights, shadows, and a small white shine dot. Notes spawn above the screen and move downward toward their matching receptor; their vertical position is based on timing difference and the selected difficulty’s scroll multiplier. Notes should be visually readable against the purple perspective-grid background.

The built-in chart should use repeating hand-authored patterns over the track: EASY uses quarter-beat alternating lane notes; MEDIUM uses half-beat subdivisions and varied lanes; HARD uses dense quarter-beat and finer patterns; ASDFGHJKL uses sixteenth-style dense notes plus occasional two-lane chord bursts. For custom tracks, chart notes should be placed from detected onset peaks, distributed across lanes, with harder modes adding chords and extra triplet/fill notes. Notes should be judged against the current song time using timing windows: PERFECT within 45 ms, GOOD within 90 ms, BAD within 140 ms. Press the four default lane keys A, S, D, F; also support tapping the corresponding canvas lane on touch devices. Pressing the correct key near a note creates a colored expanding ring at the receptor and a floating judgment label (PERFECT in gold, GOOD in green, BAD in orange). A key press with no nearby note produces only a faint ghost hit effect. Once a note passes the bad window, mark it MISS, show a red MISS label, reset combo, and reduce health.

Include a gameplay HUD: a centered top health bar initially at 50%, filled with a red/orange/green gradient; the current difficulty badge at upper left; score at upper right; a large fading combo number and COMBO label near the top center; and the song name near the bottom center. Scoring is 300 for PERFECT, 200 for GOOD, and 80 for BAD, multiplied by 1 + combo*0.02. PERFECT/GOOD/BAD slightly increase health while misses subtract 6 health. End the run if health reaches zero, or after all notes have been completed and the final note has passed. Allow Escape to pause during play, with a blurred dark PAUSED overlay and RESUME and QUIT buttons; resume should continue audio and timing, while quit returns to song selection.

On completion, show a results screen with a translucent rounded panel, a large glowing animated letter grade, the song and difficulty, final score, max combo, counts for PERFECT/GOOD/BAD/MISS, and accuracy percentage. Calculate accuracy as PERFECT=1, GOOD=.75, BAD=.25, MISS=0; assign grades S at 98%+, A at 90%+, B at 80%+, C at 65%+, D at 50%+, otherwise F, using distinct neon grade colors. Include RETRY and MENU controls.

Provide a KEYBINDS screen reachable from song selection. Show four lane rows with each lane’s colored dot and current key, clickable key buttons, and instructions to click a key to rebind or press Escape to cancel. Prevent duplicate bindings and show an explicit conflict message such as “KEY IS ALREADY USED BY LANE N”; include RESET DEFAULTS and SAVE & BACK. Persist the customized four-key mapping for gameplay labels and input. Keep all UI minimal, centered, futuristic, semi-transparent, rounded, and neon-glowing, with responsive sizing for portrait mobile screens as well as desktop.