Getting started · The tape · The code · Findings · Open questions
War in Middle Earth is a strategy game about Middle-earth: you move armies around a large map, time runs on, and now and then two units meet and there is a battle.
Everything below is measured against the binary. Anything that is a reading rather than a fact is said to be one.
The map lives at 0xCC00-0xE400 and is addressed like this:
0xCC67 + column*102 + rowwith limits of 127 columns and 99 rows (the cp instructions at 0x734B). Each cell is two by two pixels of the big map, and each colour-attribute cell covers four by four map cells (0x6AC5).
The compass is eight offsets, in the table at 0x6B34: -1, +101, +102, +103, +1, -101, -102, -103. Note that 102 is a column's stride: those are the eight neighbours. The table carries one extra entry at each end so that "direction ± 1" works without having to mask the index.
The map arrives from tape compressed, and gets compressed again before every battle to make room. That is in Findings.
Game time lives in the operands of four ld a,nn instructions, which is how this game keeps almost all its variables: 0x831C the tick, 0x8326 the day, 0x8355 the month and 0x8333 the countdown.
The game loop (0x7F6B) calls the clock every time round, and:
0x7F4F). If it reaches zero, defeat (0x83E1).At every month change it adds one to the 256 counters at 0xC300 (saturating at 255) and leaves the message "El Anillo corrompe al que lo usa." The Time panel paints it in Roman numerals: 0x8383 writes an L if the number reaches 50, an X per ten, and the units come from the table at 0x8517.
In battle the clock does not run: the loop at 0x7F57 never turns.
Bit 4 of 0xBD00+n marks the unit carrying it. 0x733E looks for the first unit with that bit set; the game loop checks whether that unit is on cell (0x68, 0x3F) and, if it is, jumps to 0x83D9. And when the bearer ends up on the same cell as another unit, 0x6A47 does set 4 on the new one and res 4 on the old, leaving the message "El Anillo se ha perdido."
(That the bit means "carries the Ring" is a reading, even if everything points the same way: what is measured is that it decides victory at 0x7F7D and defeat at 0x9218.)
When two units meet, the game builds the board on top of the menu's code: 0x5E00-0x62FF. Once a game has started, the menu and its text are scrap paper.
And the board is a draughtboard. The four movement routines (0x893E, 0x894D, 0x895C, 0x896B) always change both coordinates at once — inc b / dec c, for instance — so the parity of x+y never changes: the figures only move diagonally. Deployment rejects any pair whose parities differ, and the obstacles go on exactly the squares of the other colour.
The figures are 176 sprites of 16×8 with a mask, 32 bytes each, at 0xA2E8. They are in the gallery on the front page.
The game's text is in Spanish: "La Batalla ha comenzado", "Elige el enemigo a atacar", "No puedes atacar a un amigo", "No pertenece a tu Alianza", "Aqui no hay nadie". There are six, reached through the pointer table at 0x93D9, and the number left in 0x9190 chooses which one comes out.
The tape prompts — "Cargando Posiciones" and company — are at 0x9687, and the panel labels (File, Memo, Time, "Volver/Cargar/Salvar", "Pulsa Fuego") at 0x83F8.
The game is silent, and not for want of code: the conversion brought the Spectrum's whole sound engine across. Nothing simply ever calls it. It is measured in Findings.