Screenful Crawler

This my entry for the Screenful of BASIC 2025 Jam

It renders a first-person dungeon view and allows to walk around, including strafe left and right. On the way, it displays texts. You'll also stumble across teleporters and spinners. Find information about how it works below the images.

How it works

The first line REM statement contains the map data. 1 means wall, 0 means free area. The size is 12x12, the edges must be 1, otherwise the game will crash. 2 describes a Teleporter, 3 is a Spinner. 4 and up (including semicolon display text messages)

The second line REM statement contains all the drawing coordinates for the first-person-view elements. The values are multiplied by 8 to get to the final coordinates. These are stored in the D() Array.

DATA statements contain the translation table from map-data to first-person view.

I'll probably create a video about how the code works in general and then another one lining out the reductions to make it fit onto one screen

Changing the Map

Stop reading here if you want to explore the dungeon without any spoilers. If you're done with that, you might want to  modify and create your own dungeon.

As said above, the Map data is contained in the first REM statement. It is a 12x12 matrix. The characters have the following meaning:

• 0: Free to move
• 1: Wall
• 2: Teleport (the destination tile is defined in Line 12:  (Q=2)*-44. The "44" is the destination tile
• 3: Spinner. Changes the direction you're facing counterclockwise. This is defined in line 5 twice: F=FNF(Q=3). One is relevant when moving onto the spinner backwards/forward, the other when strafing left/right onto it.

The displayed texts can be up to 12 characters long. They are all stored in line 14. Basically, the game would display a text on every single tile, but the formula to calculate the start point of the according text only shows the following ones.

• 3: Text "Feels Dizzy!" This is displayed whenever stepping on a Spinner.
• 4: Text "Be Mindful"
• 5-9: Texts in the String in line 14. Lower digits point to texts in the back of the String. eg 5: "By Goodwell", 9: "come closer"
• Colon and semicolon also point to texts, as these come after the 9 in the PETSCII table. So these can be regarded as 10 and 11. They point to the first entries in the String in Line 14.

Have fun!