1984 · Mastertronic

Chiller

This minisite was curated by unorig, air.

The joystick and the keys, how the boy jumps from ledge to ledge, and why a fall never hurts him.

Controls

Joystick or keyboard

As the title screen says, there are two ways to play: a joystick in control port 2, or the keys Z, C, ?, and SHIFT. The game reads the joystick port itself, and leaves the keyboard to the Commodore's built-in routines.

The title screen: rescue your girlfriend from the haunted house and return to your car; use the keys Z, C, ? and SHIFT, or a joystick in port two
The title screen.
Joystick; keyboardRead asDoes
Stick (port 2) left, right; Z, C$DC00 bits 2, 3; key codes $0C, $14 in $C5walk
Stick up; SHIFT$DC00 bit 0; the shift flag $028Djump
Fire; ?$DC00 bit 4; key code $37switch players, way back only
SPACEkey code $3C, listed twice as upnothing: up is off on every screen

The key table ($4512) is part of each screen's settings, so every screen could have had its own keys. All ten have the same.

The jump

Jump to go up, fall as far as you like

The jump is 24 one-pixel steps up, each a little slower than the last, and the same steps back down in reverse. However far the boy falls afterwards, he lands unhurt.

The boy in the forest at take-off, at the top of his jump 24 pixels higher, and landed 28 pixels to the right, with a dotted line tracing his feet

One jump up and to the right in the forest, drawn by the game's own routines at three times the C64's pixels, with a dot for each frame at his feet. He rises 24 pixels in 24 frames, hangs at the top while the slowest steps run, and lands 28 pixels to the right 70 frames, or 1.4 seconds, after he took off.

Up on the stick, or SHIFT, starts a jump (start_jump, $5418) unless the boy is already falling. In the air the game switches the controls off by writing an RTS over the first byte of read_controls ($C84D), so he keeps the direction he took off in until he lands.

Jumping is the only way up. All ten screens switch off up and down as walking directions ($4500-$4503), so the boy has no climb of his own and gets up the screen one jump at a time, from ledge to ledge.

Some ledges crumble. Tiles $4D-$53 are one ledge in seven stages. Every eighth step on it moves the ledge on a stage, and the last stage is empty space (tile_touch_a, $5A9A). Stand on a crumbling ledge too long and it drops you.

A fall was once meant to hurt. The game counts how far the boy falls and compares the count with a limit when he lands, but the branch after that test has been overwritten with NOPs, and the limit is $FF anyway (land, $53EF; the limit at $457A).