akbasic/examples/breakout/sprites

Breakout, with artwork

Breakout, written entirely in BASIC for the AKGL BASIC interpreter, using downloaded CC0 sprite artwork for the paddles, the balls and the powerup gems. The bricks, the HUD and the lettering are drawn — WINDOW moves the text layer to two rows at the bottom, and everything the program draws then stays on the screen without being redrawn or captured.

The bricks are also collidable without being sprites: SOLID registers a rectangle the interpreter collides against, so sixty of them cost none of the eight slots.

../../../build-akgl/basic breakout.bas

It needs the SDL build. Without a graphics device the first SPRSAV refuses by name and the program stops there, which is the right thing for it to do.

Key	Does
left / right	move the paddle
space	start a game, launch the ball, release a stuck ball
P	pause
S	sound on and off
Q or escape	quit

Three lives, six rows of bricks worth 60 down to 10 points a row, and a field that cycles six rows, then five, then four while the ball gets faster every level up to a ceiling. A gem is worth 50 on top of whatever it does.

The powerups

A broken brick drops a gem about one time in seven, and only ever one at a time. Catch it with the paddle. The colour of the gem is what tells you which it is; the banner that flashes over the field names it as well.

Gem	Name	Does	For
red	EXPAND	doubles the paddle's width	20 seconds
yellow	MULTI	throws two more balls off the one in play	until they are lost
green	SLOW	drops the ball's speed to about two thirds	16 seconds
blue	STICKY	the ball sticks where it lands; space fires it	18 seconds
purple	CATCH	a second bar appears higher up the field	24 seconds

The second bar mirrors the paddle rather than following it, so it covers the side you just left. A second bar directly above the first is worth nothing; a mirrored one turns a dive across the field into a save at both ends.

How it works, and how to write your own

Chapter 18 of the guide builds this program step by step: loading artwork, budgeting the eight sprite slots, taking the text layer out of the way so a drawing can be seen, stamping the brick field, registering the bricks as collision geometry, the stroke font, the bounce without a square root, and the gems.

Chapter 17 does the same for ../characters, which builds the same game out of the text grid and two DATA sprites — a completely different program, and the shorter one to read first.

Where the artwork came from

Kenney's Puzzle Pack 1, released under CC0. The files in art/ are the pack's own PNG/Default/ versions, unmodified, with the pack's licence file beside them. art/PROVENANCE.md says which file is used for what and why the double-size set is not.

Crediting Kenney is not required by CC0. It is here because it should be.

What is not in it

Named honestly rather than left to be discovered:

• No music under the game, only event sounds and two four-note stings. There is room in the third voice for it; there was not much room anywhere else when it was written. The conversion gave some of that room back — the variable table is under the 128 ceiling with a handful to spare and the label table is at 57 of 64, where it was at 61.
• One gem at a time. There is one sprite slot for it. A brick broken while a gem is falling drops nothing.
• Sticky and multiball share one offset. Two balls stuck to the paddle at once sit on top of each other. It is rare enough that fixing it would cost a variable I do not have.
• No high score on disk. There is no disk.
• No attract mode, unlike ../characters. It sits on the title screen until somebody presses space, which also means it cannot test itself unattended the way that one can.

The eight interpreter defects this game turned up are filed in TODO.md §9, each with a reduction that fits on a screen and the file and line of the cause. Six are now fixed — the leaking DEF call, the skipped block that broke its caller's RETURN, the ignored subscript on SSHAPE, GRAPHIC CLR, a negative DATA item, and half of the invisible drawing. The two that stand are the left-operand arithmetic rule, which turned out to be a decision rather than a defect and is now documented as one, and the 256-line batch tear, which belongs to the host.

The listing has since been converted, and its header records what went. It used to spend two of its eight sprites on the screen itself — an SSHAPE of the HUD strip and one of the whole play field, because a drawing lasted a single frame and a sprite was the only thing redrawn for nothing. A drawing persists now, so both slots are free, the PACE routine that hunted for a frame boundary is gone with the captures it protected, and the flattened live list that made a full-field redraw cheap is gone with the redraw itself: a broken brick is erased in place.

What has not changed is the shape of the workarounds that no longer cost anything — six separate scalars for six brick stamps, loops guarded by GOTO rather than wrapped in a block. Its comments say which of the five traps still stand and which are marked FIXED.