Tycoon Tex: play

Loading the game's bytes…

Start on level

→ runs, ← slows down, ↑ jumps
Space shoots, and chooses on the menu
↑ ↓ move through the menu
J or K on the menu chooses the joystick or the keyboard
P pauses (the C16's SPACE), C carries on (C=)
Esc ends the game
Z X ; / Enter are the game's own keys, with the keyboard chosen

The game's own screen, drawn from the port's memory as TED would draw it, line by line: the five bands the raster interrupt makes, each with its own colours and scroll. The arrows and Space are a joystick in port 2, or the game's own keys when the menu is set to the keyboard. The game starts with its sound off; Start again and Start on level set SOUND to ON on the menu while the page's sound is on, and keep the lives, the difficulty and the controls you chose. Start on level plays the game's own way there: PLAY THE GAME, then each level before it finished at once, as Plus/4 World's poke of $9D does, so the score holds those levels' bonuses, and waits, paused, when it gets there. The two cheats are Plus/4 World's pokes, made in the game's memory as a monitor would make them.

01 · Differences

What differs from a Commodore 16

The loading. There is none: the page starts where the Novaload loader hands over, at the game's first instruction at $1800, which fills the skyline and the pipeline and goes to the menu.
The KERNAL. The game takes TED's raster interrupt through the C16's ROM, which saves the registers and jumps through the vector at $0314; the game's handler puts the registers back and returns by itself. The page does not carry the ROM. It calls the game's handler itself and charges the ROM's cycles on the way in. The game's one other call into the ROM, at its start, clears the screen; the page fills the screen with spaces, as that call does.
The screen. TED reads the screen as its beam meets it. The page keeps the memory as each row of characters began and TED's registers line by line, a write taking effect on the line after the one it was made on, and draws the frame from those. The game's raster interrupt changes the colours, the fine scroll and the character set five times a frame, for the HUD, the skyline, the play field, the pipe and the message row. The port makes each of those changes as its interrupt is taken, and the page puts each on the line where the game's own lands, from the cycles the game takes to reach it.
The interrupt. On the C16 the raster interrupt can come between any two instructions. On the page it comes between the port's steps: at each call main_loop makes, at each turn of a loop that waits, and where the game lets it in itself, during Tex's death and as a level begins. The game's main program reads 17 bytes that the interrupt writes, among them the controls, the random numbers and the flags for a death, a pause and a finished level. On a C16 one of those can change between two of its reads; on the page it cannot.
Random numbers. The game stirs its random numbers with TED's timers, read as the code reaches them. The page reads them on its own clock, so the enemies come and the breaks fall where a C16 would put them on some other run, never where one particular run did.
The sound. The game's writes to TED's sound registers go to the site's model of TED's two voices, made from the plus4emu emulator's, each write at the place in the frame where the page's clock made it. The game loads with SOUND OFF on its menu. While the page's sound is on, Start again and Start on level turn it on the way a player would, on the menu.
The joystick. The game reads the joystick in port 2, or in port 1 when port 2 shows nothing. The page's stick, the arrows and Space or the pad on a touch screen, is in port 2.
Start on level. The game has no way to choose a level. The page's buttons play the way there: on the menu they choose PLAY THE GAME, then each level before the one wanted is finished at once, as Plus/4 World's poke of $9D does. Each level gets its scene, its enemies and its pipe from the game's own next_level, and the score holds the bonus for each level finished, the pressure left on a full pipe. The page then waits, paused, for an arrow, Space or a click, since on the later levels the enemies come within a second. The high-score table lasts until Start again or another level, which start the game from its first instruction.
The cheats. Unlimited lives and Tex can't be hurt are Plus/4 World's pokes: the page writes the same bytes into the game's code (cheats.md), and the port reads its instructions there, so the game does what it does on a C16 with the same pokes.
The keys. The arrows and Space are the joystick, or, with the keyboard chosen on the menu, the game's own keys: Z, X, ; and / with RETURN to fire. The C16's SPACE pauses the game and C= carries on; on the page they are P and C, since Space fires. Enter is RETURN and Esc is ESC.