Hotaru - Live Penlight

Hotaru is a virtual penlight app that lights up both your iPhone and Apple Watch — for concerts, festivals, sports games, and any moment that calls for cheering.

Keep your phone in your pocket and change colors right from your wrist. Just rotate the Digital Crown to cycle through 16 colors. Even in the darkest venue, every control happens at your fingertip.

【 Features 】

■ Apple Watch as the main control
Raise your wrist and rotate the crown to switch colors. The Apple Watch screen itself glows in your chosen color, working as a small penlight on its own. Single-tap to light up, double-tap to turn off, long-press for an immediate blackout.

■ 16 curated colors
Snow, Crimson, Coral, Tangerine, and more — 16 refined colors that shine at the venue, cycling smoothly with the crown.

■ Show your message inside the penlight
Display the name of your favorite, a heartfelt message, or any text you love — right inside the penlight. Short messages appear large and centered; longer messages scroll smoothly like an LED message board. Mix Latin letters, kanji, hiragana, katakana, and emoji in any combination. Beautiful LINE Seed JP Bold typography. Tap any of your 8 most recent entries to reuse them instantly.

■ Vertical / Horizontal text (v1.4 new)
Toggle between Japanese-style vertical writing and Western-style horizontal layout right from the input sheet. Match the style to your show — a traditional Japanese live atmosphere or a clean, social-media-ready look.

■ Landscape LED ticker mode (v1.4 new)
Set your phone down sideways and the penlight transforms into a horizontal LED ticker. Perfect for stadiums, festivals, and marathon cheering — anywhere you want your message to be seen from a distance.

【 Beyond concerts — sports & cheering 】

Hotaru is not just for live music. The 16-color palette and LED ticker mode shine just as bright at:

· Baseball stadiums — pick your team's color and rally with chants
· Soccer / football matches — display your player's name or number
· Marathons — cheer your runner with their name from the roadside
· Festivals & school events — light up the crowd in your team's color

Whatever you want to cheer for, Hotaru turns your phone into a personal cheering tool.

■ Brightness lock
In fullscreen mode, the app overrides iOS auto-brightness and locks at a fixed value. Match the brightness of other penlights in the venue. Adjust the maximum from the Settings tab.

■ Dark UI
Bright white screens can be distracting in a venue. Switch to Dark in Settings and the entire UI goes low-light, while the glow color in fullscreen mode stays unaffected.

■ Built-for-the-dark haptics
Every action provides tactile feedback so you never need to look down.

■ Safety reminders
A drop-prevention modal appears on first launch, and a wrist-strap reminder pops up before entering fullscreen mode.

【 Privacy 】

· No ads
· No signup (no email, no social login)
· All data stays on your device
· Zero third-party SDKs, zero analytics

【 Before you use 】

Please check your venue's smartphone usage rules before use. Always attach a wrist strap (or similar drop-prevention accessory) and slip it onto your wrist before swinging. The developer assumes no responsibility for any accidents or damages resulting from the use of this app.

【 About 】

KARABINA LLC (Tokyo, Japan)
A small studio building utilities for live show fans.