Hotaru - Live Penlight

Turn your phone into a virtual penlight for concerts. Control it from your wrist — no ads, no signup, no data collection. Free forever.

Hotaru is a virtual penlight app that lights up both your iPhone and Apple Watch for live shows and concert venues.

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 muted, refined colors that cycle 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.

■ 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.