Platoon

01 · The game

Five men in Vietnam

The loading picture, shown while the first load comes in.

The player leads a platoon of five soldiers, one man at a time, through the film's story in four parts. In the jungle they find explosives and blow up a bridge, then search a village for a torch and a map that lead to the tunnels. Under the ground they look for flares and a compass, then hold a dugout through the night. Last comes a jungle maze against the clock, with Sergeant Barnes waiting in his bunker.

A man who takes four wounds is out, and the CHOOSE YOUR MAN panel brings on the next. When all five are gone the game is over.

The first screen of the jungle, with the status panel below it.

02 · Structure

Four programs on one disk

Each section is a separate program of about 56 KB that fills the machine from $0400 to the top of memory. A one-kilobyte loader file on the disk (LAY1, LAY2 or LAY3) brings in the next. Every program carries its own copy of the music driver at $E000, its own raster interrupts and its own title and end screens, so nothing is kept from one section to the next but the disk itself.

03 · Section one

The jungle, built from blocks

The jungle and the village are one map at $A000: 20 rows of 90 block numbers. A block is 8 characters across and 6 down, stored at $8000 + 48 × its number, so one screen is five blocks wide and three high. As the soldier walks, the screen scrolls a pixel at a time and $B70B or $B7BA decodes one new column of characters from the map. The Maps tab draws the whole map.

Climbing a ladder moves the map position three rows up or down ($2A09), and a ladder down from a hut leads to the entrance of the tunnels. The bridge is two blocks, $8C and $8D; setting the explosives swaps them for the broken blocks $95 and $96. Walking on to the place where the bridge stood drops the soldier into the river ($3D38), and if the bridge is still standing when the patrol arrives ($3B25) the game is over.

Enemies walk in from either edge on a timer whose gap shortens by one each time, down to five passes ($1EC7). What each one does next comes from 22 short scripts of actions at $259E, picked by a random number: walk, jump, fire, or crouch and shoot back when the soldier fires. In the village the figures are villagers, and shooting one gives the message YOU SHOULD NOT KILL INNOCENT VILLAGERS.

Searching a hut ($CC8D) looks the soldier's place up in 19 ranges of the map and shows what is there: a sack of flour, a pot of rice, the torch, the map, or a booby trap. With both the torch and the map, the trapdoor asks DO YOU WISH TO GO DOWN, and fire loads the next section.

04 · Lives

Five men, four wounds each

The CHOOSE YOUR MAN panel, opened when a man is lost.

A hit costs three points of morale, four once morale is below 43, and adds a wound mark to the panel ($BD56). When a man is lost, $BFB8 saves his wounds, grenades and magazines into his row of the table at $F69F and opens the CHOOSE YOUR MAN panel, where the cursor moves over the five slots and fire picks a man ($C157). A man with four wounds cannot be chosen, and when all five have four the game is over.

Ammunition is counted in magazines, eight shots each, drawn as half and whole icons on the panel ($BCCB). A dead enemy may leave supplies on the ground: 300 points, two more magazines, a wound taken back and four points of morale ($3A88).

05 · Section two

The tunnels in first person

The tunnels are seen from the soldier's eyes, with a small map in the corner. The map is a grid of squares, tunnel or water or rock; forward and back step one square, and left and right turn ($09F1). Each step scans up to four squares ahead for walls, water and side passages ($10A0), and $1260 draws the view from two picture halves of 10 by 18 characters chosen by what the scan found.

Ten squares are rooms ($15DC). Each has boxes on its picture, and firing at a box with the crosshair takes what it holds: flares, the compass, Viet Cong ammunition or medical supplies ($19D1). While the soldier walks, the counters at $0725 start Viet Cong attacks from ahead or from a side passage. Shooting the attacker scores 300 points; if his knife reaches the end of its frames, the man is killed.

06 · Section two, continued

A night in the dugout

With the flares and the compass, the soldier reaches the dugout ($1A21) and has to hold it until dawn. Enemies rise and duck in the dark, and a flare ($1D7B) climbs and burns through nine stages that light the screen and show the enemies ($1E50). At dawn the game shows WELL DONE! SECTION COMPLETED, scores 5,000 points and loads the last section.

07 · Section three

A maze of 120 jungle rooms

The last section is a maze of rooms on a grid ten wide and twelve high ($3590). Each room is drawn from one of a few maps of 30 by 25 characters, then trees, huts and the bunker are added from its own list of shapes ($3634). Walking off an open edge moves to the next room, and the panel's compass arrows show which edges are open ($3905). The Maps tab draws every room.

The section runs against a clock that starts at two minutes ($1B87). Mines and tripwires wait in the rooms, a sniper fires from the trees ($22E0), and in the bunker Barnes takes five hits before he falls ($16A9). Running out of time or men ends on YOUR PLATOON HAS BEEN DESTROYED; beating Barnes ends on the honourable discharge, worth 30,000 points ($C06A).

While a man is wounded, a heartbeat plays as a sample through the volume register, faster for each wound ($F000).

08 · The cheat

Z, A, C, H, and 1

Every frame of the first section, the main loop at $07B5 tests whether Z, A, C, H and 1 are held together. With all five down it writes rts over the first byte of $2BC8, the test of whether an enemy has caught the soldier or an enemy bullet has hit him, so neither can kill him; N puts the routine back. The letters are the first name of the programmer, Zach Townsend. The Discoveries tab says what the cheat leaves out.

09 · Reception

Reception

Zzap!64 gave the Commodore 64 version 94%, praising it as a faithful film licence.¹