Hotaru turns your smartphone into a glowing pen-light. For every moment you want to cheer — concerts, live shows, baseball stadiums, soccer matches, marathons, and more.

Pick your favorite's color from 16 presets and tap "Light up fullscreen." Your whole screen becomes a pen-light. No ads, no sign-up, completely free.

[Features]

■ 16 color presets
Snow, Crimson, Coral, Tangerine and more — 16 refined colors that shine at the venue. Swipe left or right while lit to change colors.

■ Show a message inside the pen-light
Display your favorite's name, a heartfelt message, or any text inside the light. Short text appears large and centered; longer text scrolls smoothly like an LED ticker. Mix kanji, kana, Latin letters, and emoji freely. Tap any of your last 8 entries to reuse it.

■ Vertical / horizontal writing
Toggle between traditional Japanese vertical text and Western horizontal text in the input sheet.

■ LED ticker mode (landscape)
Turn your phone sideways and the pen-light becomes a horizontal LED ticker — perfect for stadiums, ballparks, festivals, and marathons where you want your message seen from afar.

■ Pen-light mode
A glowing-baton display mode. Tilt your device and the light sways for a realistic pen-light feel.

[Not just concerts — cheer at sports too]

- Baseball — wave in your team's colors to the fight song
- Soccer / stadiums — show a player's name or number
- Marathons — raise a runner's name from the roadside
- Sports days & school festivals — light up in team colors

■ Brightness lock
In fullscreen mode the brightness is locked to a fixed value so it blends with other pen-lights at the venue. Adjust the limit in Settings.

■ Dark mode
Switch to Dark in Settings to keep the whole UI low-light, so you won't disturb others in a dark venue. The lighting color itself is unaffected.

■ Safety first
A drop-prevention notice is shown on first launch.

[Privacy]

- Zero ads
- No sign-up (no email / social login)
- Data stays only on your device
- Zero third-party SDKs, zero analytics

[Before you use]

Always check the venue's rules on smartphone use. Always attach a strap or other drop-prevention device and keep it around your wrist. The developer assumes no responsibility for accidents or damages resulting from use of this app.

[Developer]

KARABINA LLC (Tokyo, Japan)
We build small utilities for live-event fans.

KARABINA, LLC

Additional Information