CHix

Trailer (32 s, from the PC simulator, with the game's own soundtrack): docs/CHix-trailer.mp4

An original arcade game for CHGame: draw lines out into the open field, close them back on a border and claim the ground behind them, while a spinning enemy and its sparks hunt for your open line. Forty-five stages, ten rainy cityscapes, ten power-ups and a psytrance soundtrack on a small FM synth. It is in the spirit of the territory-claiming arcade classics; every line of code, picture, sprite and tune in this repository is original.

Controls

Control	Action
D-pad	Move along the border; steer a line you are drawing
A + d-pad	Draw a fast line (blue, 10 points a cell)
B + d-pad	Draw a slow line (orange, 20 points a cell)
START	Pause menu: resume, save game, return to title
START (hold 3 s)	Back to the CHGame menu

Rules

• Walk the border. Push into the open field with A or B to draw a line; reach any border to close it and claim the side without the main enemy.
• Claim the stage's share of the field (70% at stage 1, 2 more every stage, then 85% from stage 9 on) to clear it. Bigger claims score more, and a slow line is worth double. Claim again within eight seconds and the score multiplies, up to x5.
• The enemy kills you if it touches your open line. A spark kills you if it touches you. From stage 4 a fuse burns down your line if you stop drawing for a moment.
• Three lives, and an extra one at every 10,000 points. A spark caught inside a claimed area explodes for 1,000.
• Clear stage 45 to win.

Enemies

Stages 1 to 25: eight main enemies come round in turn: the roaming line, cube drone, octa core, pyra scout, prism hunter, hex warden, icosa mind and tesseract. The core gets faster, the sparks speed up from stage 6, and a third spark joins at stage 8.

Stages 26 to 45 are harder. Five new solids (star core, ring warden, cubocta, spire lord, cross gate) come first. From stage 31 the enemy is a twin pair, one solid at each end of the line, spinning out of step: either can kill you, and a twin caught inside ground you claim blows up for 3,000 and returns beside the other. A fourth spark joins at stage 30, the sparks run faster from stage 36, and the last stages end on twin tesseracts.

Power-ups

Pick-ups appear in the field and are collected by drawing onto them or closing round them. New ones unlock as you go.

Power-up	Effect	From stage
Time freeze	The enemy stops and cannot hurt your line	1
Speed up	A whole cell a frame; slow lines at full speed	1
Lasers	Beams along your row and column send sparks away	1
Shield	Nothing can hurt you	1
Slow	Enemies move at half speed	1
Bonus	+2,500 points	1
Score x2	Double points	5
Ghost trail	The enemy cannot hurt your line	9
Bomb	Destroys every spark for 1,500 points	13
Extra life	One more life	17

Saving

The game saves at the start of each stage and from the pause menu (SAVE GAME). The title offers CONTINUE or NEW GAME when a save exists. A continued game restarts its stage with the saved lives and score. The best score is kept too.

Building

You need the CHGame board package and a CHGame board. From this folder:

./cl build      # build
./cl upload     # flash it to the board

dist/CHix.CHG is the packed game for the CHGame SD menu. The game needs CHIX.DAT (dist/CHIX.DAT, 198 KB) in the root of the SD card: the painted stage pictures, title and menu screens, sprites and animations are read from it. Without it (or with another build's) the game shows "NEED CHIX.DAT" and checks again every second. python tools/make_card.py rebuilds it from tools/paint/ (and rewrites CHix/CardIndex.h; rebuild the game after).

Developer notes

• CHix/CHix.ino is the whole game: one sketch, integer maths, drawing straight into CHGfx's framebuffer.
• The playfield is a 60x56 grid of 2x2-pixel cells. A claimed cell shows 2x2 pixels of its stage's painted 120x112 picture, read from CHIX.DAT each frame in one multi-block DMA read (CHix/Card.cpp) together with the sprites the frame draws, each 512 B block drawn while the next arrives; a slow claim shows a thin gold sheen. Each stage's palette comes from its picture, with palette effects (lightning, fade-in, shimmer, neon flicker: docs/FX-SPEC.md), rain at three depths and flying cars drawn over it. Border flags are cached in the grid, so a frame does no neighbour scans.
• The art lives in tools/paint/ (scenes, title.png, screens/, sprites/, anim/, each with its painting script) and tools/make_card.py packs it: every sprite and animation frame is remapped to the nearest colours of each scene's palette. Full-screen pictures (title, pause menu, clear, game over, win) are copied to the frame buffer with their own palette. The songs and shapes are generated by tools/make_music.py and make_shapes.py into the headers in CHix/; the old procedural art generators (tools/gen_art.py, make_sprites.py, make_bosses.py) are kept for reference, with their headers in tools/old_art/.
• Not done: the parallax scroll (docs/PARALLAX-SPEC.md), the HUD picture, the level intro screens and the blimp, radar, steam, ripple and sign animations.
• The sound is a small software synth (CHix/Synth.cpp): a timer interrupt mixes three 2-operator FM voices (a bell lead, a pluck bass and a glassy arpeggio) and a drum voice into the piezo as 8 kHz PWM, and the game's effects play on top as a square voice. The nine songs (downtempo dub for the title; stages 1 to 25 cycle aurora, dark psy, goa, full-on and forest, calmest to most frantic; stages 26 to 45 cycle progressive, nebula and hi-tech; the title, aurora and nebula are ambient at 80 BPM) are 16-bar step sequences (tools/make_music.py, 1 KB each), each with its own FM sound.
• Measured on the board (./cl run --device CHix/tools/scripts/perf.txt out/perf, -D CHIX_START_LEVEL=n for a later stage, CHIX.DAT on the card): about 16 ms a frame, 17.8 ms at worst, (stage 45, with twin tesseracts and four sparks: about 19.5 ms, 23.8 ms at worst). Since 1.5.0 the game runs at 40 fps, which allows 25 ms a frame. GFX_CHUNK_ROWS=1 (in CHix/tools/game.py) gives back about 500 B of RAM.
• Budgets: the image must stay at or below 50,432 B so both save pages survive, and static RAM is nearly full.

Credits and licence

Game, art, music and code: Jadflat, MIT (see LICENSE).

The stage pictures, title and menu screens, sprites, boss cores and animations (tools/paint/) were painted by this repository's own scripts, with Claude as the artist, and checked with CHGame's artkit.craft against its pixel-art rules (docs/pixel-art.md in CHGame). They are original and covered by the MIT licence.

The sound output (an 8-bit PWM written by a timer interrupt) follows the design proven by chgame-soundtracks in ESPboy-edu's ESPboy_CHCore (BSD 3-Clause; see THIRD-PARTY.md), and CHeleste's software mixer showed it was practical (no code taken). The synth, songs and sequencer on top are CHix's own.

Built on CHGame, Copyright 2026 Kevin Bates (bateske), Apache-2.0: the framework is vendored in chgame/ (see chgame/NOTICE and chgame/LICENSE).