Tetris
About this app
Tetris is a minimalist implementation of the iconic block-stacking puzzle game, built natively for the CASIO ClassPad II using the Hollyhock-3 SDK. Arrange falling tetrominoes to complete horizontal lines, clear them from the playfield, and rack up points as the pace gradually increases. A faithful, no-frills experience optimized for calculator hardware.
Features
- Classic tetris mechanics: all seven standard piece types with four-way rotation
- Responsive controls: move, rotate, and soft-drop with immediate input response
- Dynamic difficulty: drop speed increases as your score grows
- Line-clear detection: automatic row removal with cascading block updates
- Efficient rendering: palette-based drawing with direct LCD access for smooth updates
- Lightweight design: minimal memory footprint suitable for embedded calculator environments
Controls
| Key | Action |
|---|---|
| ( | Rotate Piece Counter-Clockwise |
| * | Rotate Piece Clockwise |
| 4 | Move Left |
| 6 | Move Right |
| 5 | Soft Drop (hold to accelerate descent) |
| POWER or CLEAR | Exit Game |
Rotation includes collision validation: if a rotated piece would intersect walls or placed blocks, the rotation is reverted to maintain gameplay integrity.
Playfield Specifications
- Grid dimensions: 12 columns by 22 rows
- Block size: 20x20 pixels with 1-pixel grid lines
- Visible play area offset: 40 pixels from screen edges
- Color palette: 8 entries, with piece types mapped to distinct colors and white used for erasure during animation
Scoring and Progression
- +1 point for each piece successfully placed
- +10 points for each completed line
- Drop interval decreases as score increases: base wait of 16 frames reduced by score divided by 64
- Game ends when a new piece spawns into an occupied position at the top row
Installation
- Download the tetris.hh3 file from the official repository
- Copy the file to the root directory of your ClassPad II storage
- Launch the Hollyhock-3 application menu and select Tetris to begin
Requirements
- CASIO ClassPad II (fx-CP400 or compatible model)
- Hollyhock-3 custom firmware
- Approximately 600 KB free storage space
Technical Implementation
- Piece definitions stored as coordinate offsets relative to a pivot point
- Rotation performed via 2D coordinate transformation with collision rollback
- Pseudo-random number generator uses a simple XOR-based algorithm seeded by initial key presses
- Screen updates use double-buffer style erase-and-redraw to prevent visual artifacts
- Score display rendered via debug console overlay at screen top
Tips for High Scores
- Keep the playfield flat to maximize placement options
- Reserve the soft-drop key for precise positioning in tight spaces
- Plan rotations early to avoid last-second collisions
- Monitor the increasing drop speed and adjust your rhythm accordingly
Troubleshooting
If the game does not appear in the launcher, confirm the .hh3 file is placed in the calculator root directory and not within a subfolder. If input responsiveness seems inconsistent, ensure no background processes are interfering with the input handler. The game exits cleanly via POWER or CLEAR; in rare cases of system lockup, a battery removal will reset the device without affecting stored user data.
Development Notes
This implementation was authored by De_Coder as a demonstration application for the Hollyhock-3 SDK. The code prioritizes readability and educational value, serving as a reference for game loop design, collision detection, and direct hardware rendering on the ClassPad platform. Source code is available in the official repository for study and modification.