The game

Ale Hop! is an obstacle race. You steer a grinning ball down six horizontally scrolling tracks, jumping whatever gets in the way and picking things up, with the clock against you.

The credits come from the game's own title screen, reconstructed by decompressing the graphics out of the binary:

PROGRAMA: ALBERTO L. NAVARRO GRÁFICOS: LUIGILOPEZ TOPO SOFT 1988

How the screen is put together

The three horizontal bands aren't a design flourish — they're the three the MSX SCREEN 2 mode hands you. That mode splits the display into three eight-row thirds and gives each its own pattern and colour tables, which is how you get 768 distinct tiles on screen instead of 256.

rows	what goes there	source
0-7	The background, with parallax	64x8 map at 0x3000 + level*0x200
8-15	The playable track	256x8 map at level*0x800
16-23	The scoreboard	fixed 32x8 map at 0x4500

Parallax in one instruction

The background moves slower than the track, and the trick fits on one line. Both blit routines read the same variable — the camera column at 0xDB54 — but:

• the track's uses the whole byte, and its map is 256 columns wide;
• the background's does and 0x3F on it, and its map is 64.

The background therefore walks its map four times slower. Depth, for free.

The six levels

Each level is a 256-column strip of which you only ever see 32. Laid out whole, this is level 1:

In each map byte, the low 6 bits say how the tile behaves and the top 2 pick which of four graphics banks it uses. That's why every level looks like a different game even though the engine is identical: the bank changes, the code doesn't.

There are 15 terrain classes, derived by comparing the low 6 bits against a threshold table at 0xDACE:

0C 10 14 18 19 1A 20 22 24 26 28 32 38 3E FF

Nine of those classes have consequences. Some tiles stop you dead — the camera snaps back 40 columns — others are collectibles worth 375 points that vanish when touched, some add time, one grants an extra life up to a maximum of four, and some kill you.

The controls

• Left and right don't move you: they change your speed, which runs from 0 to 38 and lives at 0xDB60. It's a racing game, not a platformer.
• Up and down move you diagonally across the track.
• Space or fire jumps.

Input goes through GTSTCK, checking the cursor keys first and then joystick 1, so both work.

The main character

The ball is a multicolour sprite on a machine that doesn't have them. The MSX1 allows exactly one colour per sprite, so the game stacks three sprites — one per colour: black, white and light yellow — at the same position. All three are rebuilt every frame, reading their colours from 0xDB6E.

The bouncing ball on the title screen uses the same trick.

The scoreboard

Seven score digits, the character's face, and a timer. The panel is a fixed map blitted once when the stage starts; the digits are written on top of it.

And if you finish it

Clear level 6 and you get a screen with a scrolling message:

ENHORABUENA!!! HAS CONSEGUIDO SUPERAR LOS OBSTACULOS QUE TE SEPARABAN DE LA VICTORIA... TOPO SOFT TE FELICITA. PERO... PODRAS CON TEMPTATION??

("Congratulations!!! You've overcome the obstacles that stood between you and victory... Topo Soft congratulates you. But... think you can handle Temptations?")

The text isn't drawn into the screen: it's written at runtime, letter by letter, by a smooth-scrolling routine. And the sign-off is an ad for another game Topo Soft had released the year before.