Scratch

Project Notes

The Japanese navy is in retreat and you have been left behind to disrupt the enemy onslaught. You captain a top of the line attack submarine, when on the surface, it can outrun all but the fastest of the enemy ships. Your mission: stop as many of the enemy ships as possible with the torpedoes at your supply base. The enemy is steaming South, how many of their ships can you sink? Arrow Keys control Throttle and Rudder "P" toggles Sonar Pinging "D" toggles Dive/Surface "Spacebar" to Launch a Torpedo If you are on the surface or are "pinging" when close to an enemy ship, you will be spotted and a Destroyer will be called in to hunt you down - use active sonar and surface running carefully! Your sub can carry 4 torpedoes, you must return to your base (within the boundary of the dashed line) to rearm the sub. Ships that make their way south of your home island are considered to have "escaped"... Credits: Thanks to the "Freesound Project" for the various sounds of the sub, torpedo and the scout airplane. Also, many thanks to "The Guardian" for the elegant "digit" code used to display the score/torpedo count/ships escaped, and to the Scratchers whose comments and ideas helped to make SubHunt a better game as work progressed on it. Tech Notes: Because of the limited screen size of Scratch, the game needed to be a scroller. "Scrolling" is accomplished by moving the islands (and ships) over the blue "stage". Each sprite maintains its own "World_X" and "World_Y" variable in response to its velocity, and its display position is maintained by finding the difference between its world coordinates and the Submarine's. The submarine is normally displayed in the center of its own "Sonar Screen", but when a torpedo is launched, it moves from "home", in the direction opposite the torpedo, to give the effect of having the "camera" follow the torpedo. This lets you shoot at a target that is running away and about to go off-screen, yet still see the results of your shot. The world positions of the islands and ships are scaled to allow them to be represented by similarly scaled sprites in the Sonar Screen. These positions are used to avoid collisions with islands and to monitor the distance from the ships to the scout plane. If close enough to the scout plane, the sonar image of a ship will go from a ghost effect of 99%, down to zero (fully visible), then gradually fade as its position becomes uncertain.