i-20000

About the game

i-20000 is a horizontal shooter in which you command a small submarine. Its title comes from the Japanese original, 伊, the character used to name Japanese submarines; the studio Planet Marimo first made it for Windows and then ported it to the Arduboy themselves, releasing this version as free, open source software.

The twist is that the battlefield is three screens wide and you only see the first one. Enemy ships move around in the two screens of open water ahead of you, out of sight. Dots blinking along the right edge of the screen are your sonar: they show roughly where the enemies are. Small ships that come close are handled by your machine guns, which fire automatically whenever there is a target on screen. The big ships can only be sunk by torpedoes, and you have just one in the water at a time.

A torpedo can travel into the unseen area and hit a ship there, and a hit far away is worth more. A miss, though, gives away your position, and the ship you aimed at turns towards you. The enemies arrive in waves; every six waves the zone number goes up and the attacks get fiercer.

Playing it here

This is a homebrew game for the Arduboy, the open, credit-card-sized handheld with a tiny black-and-white screen: a version made by the original developers for the device, not a commercial release. It runs here in Ardens, an Arduboy emulator. Click Play, then press Z on START.

The title menu also lets you switch the music and sound effects on or off and look at the ranking of the five best scores. When you make the ranking, you enter three letters with the arrows and Z, then pick the mark in the bottom right corner to finish. The ranking is stored in the emulated memory of the Arduboy, which is kept in this browser automatically. F2 saves the complete state of the game at any moment and F4 brings it back. A gamepad works too.

Controls

Scoring

• A small ship is worth 1 point, and wiping out a whole formation of them adds a 10-point bonus.
• A big ship is worth 10 points, plus up to 10 more the further away it was when the torpedo hit.
• Every 500 points gives you an extra submarine. You start with two spares, shown in the top left corner.

Tips

Fire early. The sonar dots tell you which line a big ship is on; a torpedo launched before it comes into view scores more and keeps it from ever getting close.

Make every torpedo count. Only one can be in the water at a time, and a miss brings that ship straight at you, so line up before you launch.

Let the guns work. You never need to aim at the small ships; keep the submarine where they will cross the screen and the guns take care of them.