This repository is a Python application/library for generating 2D heatmaps from coordinate data. The core module src/heatmap77/heatmap.py implements a complete pipeline: file readers parse plain text, CSV, GPX, and ESRI Shapefile inputs; coordinate systems and projections (equirectangular, mercator) map lat/lon to pixel space; linear and gaussian kernels spread point mass; sparse matrix classes accumulate contributions with optional decay; and an ImageMaker renders the result to PNG/PPM, optionally compositing over OSM tiles or custom backgrounds. The package exposes both a CLI entry point (heatmap77) and a programmatic API used by the examples.