The joystick

Up is the jump, and fire swaps the Goonies

The game reads the joystick in port 1 once a pass, at the top of the main loop ($08EB). The controlled Goonie's routine copies up onto the fire bit before move_object sees it ($0B14), so up does what most games give to fire: it jumps from a floor, climbs a ladder, and grips a bar.

Stick	What the Goonie does
Left, right	walks two units, four pixels, a pass
Up	jumps straight up from a floor; climbs a ladder; holds on to a bar
Up-left, up-right	jumps diagonally, two units across a pass
Down	climbs down a ladder, or through a floor that is a ladder's top; lets go of a bar
Fire	gives the stick to the other Goonie (one player)

Fire is read as a press, not as held. The main loop sets a flag on the pass fire goes down and not again until it has been let go ($0976), and the waiting Goonie's routine swaps the two Goonies' types on that pass and plays sound 6 ($0B62).

Two players

Two players play at the same time, with a joystick each

F3 on the title switches two players on and off and shows a 2 in the corner of the status line ($169C). A game started that way gives each player a Goonie: the first object slot reads port 1 and the second port 2 (read_stick, $172B), and fire no longer swaps anything.

The C64-Wiki describes the standard game as two players taking turns, and gives this simultaneous mode to the U.S. Gold release alone.¹ The Datasoft disk analysed here has the simultaneous mode and no turns.

The keys

L turns a player's joystick a quarter turn

The game scans eight keys ($161C) and acts on a key the pass it goes down (handle_keys, $1634).

Key	Where	What it does
F1	$1684	quits to the attract mode
F3	$169C	one or two players, on the title only
F7, or fire on the title	$168B	a new game, from the scene in $12BC: always scene 1
Space	$165F	pause, with PAUSED on the status line, music and effects silent
S	$16B6	music off and on
V	$1692	prints the version line, V 1 BY SES
L, shift L	$16C2	turns player 1's joystick, or with shift player 2's, a quarter turn, marked 1L or 2L on the status line
F5	none	scanned with the others, and nothing acts on it

The L key changes how read_stick reads the port ($1742). With it on, pushing left reads as up, right as down, up as right, and down as left, so a joystick held on its side works the right way round. Fire is left alone. Why the game offers this is not known, and the C64-Wiki does not list the key.