Add transparent background mode and HH:MM:SS timer display

[NoamFav]

Add transparent background mode and HH:MM:SS timer display

Summary

This PR builds on #65 by @naivecynics, adding an optional transparent background mode to nyancat, upgrading the timer display from seconds to HH:MM:SS format, and applying minor code formatting improvements. All changes are backward-compatible, with new behavior activated via command-line flags.

Changes

1. Transparent background mode (-T, --transparent)

Implements the transparent background feature originally proposed in #65, allowing nyancat to render without a solid background color.

Implementation:

• Adds global flag transparent_bg (default: 0)
• New CLI option: -T / --transparent
• Integrated into getopt_long options:

  static struct option long_opts[] = {    ...    {"transparent", no_argument, 0, 'T'},    ...};
  

• Conditionally maps background color to transparent:

  if (transparent_bg && ttype != 6 && ttype != 7)    colors[','] = "\033[49m";  // Use terminal default background
  

• Excludes ttype 6/7 terminals to preserve existing color expectations
• Updates usage() documentation

Benefit: Enables seamless visual integration with terminals using custom or image-based backgrounds.

2. Enhanced timer: seconds → HH:MM:SS

Replaces the basic seconds counter with a human-readable time format for longer nyan sessions.

Before:

printf("\033[1;37mYou have nyaned for %0.0f seconds!\033[J\033[0m", diff);

After:

int total = (int)diff;
int h = total / 3600;
int m = (total % 3600) / 60;
int s = total % 60;
printf("\033[1;37mYou have nyaned for %02d:%02d:%02d!\033[J\033[0m", h, m, s);

• Properly handles sessions lasting hours
• Adjusted centering logic for fixed 8-character format (HH:MM:SS)

3. Code formatting and cleanup

Minor cosmetic improvements for consistency (no behavioral changes):

animation.c:

• Normalized array declarations (opening brace on same line)
• Compacted frames pointer array for readability

nyancat.c:

• Improved indentation consistency
• Cleaned up include statement ordering

Review tip: Use GitHub's "Hide whitespace" view (?w=1) for easier code review.

Testing

Verified across multiple scenarios:

Command | Expected Behavior | Status -- | -- | -- ./nyancat | Default rendering (unchanged) | ✅ ./nyancat -T | Transparent background + timer | ✅ ./nyancat -n | No counter display | ✅ ./nyancat -T -n | Transparent + no counter | ✅

All tests confirm:

• Animation renders correctly in all modes
• Transparent mode uses terminal's native background
• Timer displays accurate HH:MM:SS elapsed time
• No regressions in existing functionality

Backward Compatibility

• ✅ Default behavior unchanged when no flags provided
• ✅ Transparent mode is opt-in via explicit -T flag
• ✅ All existing options work as expected

Credits

Transparent background feature concept and initial implementation by @naivecynics in #65.