Move demos to examples folder, compile multiple targets in that folder

Makefile

@@ -1,38 +1,45 @@
 CC = gcc
-TARGET = demo 
 SRC_DIR = src
 INC_DIR = include
+# This is where the targets will be compiled from
+EXAMPLES_DIR = examples
+TEST_DIR = test
 CFLAGS = -g -I$(INC_DIR) -Wall
 LDFLAGS = -lm
-DEMO_SRC = main.c 
-TEST_SRC = test/test.c
-SRC = $(wildcard $(SRC_DIR)/*.c) $(DEMO_SRC)
+TEST_SRC = $(wildcard $(TEST_DIR)/*.c)
+EXAMPLES_SRC = $(wildcard $(EXAMPLES_DIR)/*.c)
+# Each demo source gets a target, e.g. examples/01_demo.c -> 01_demo
+EXAMPLES = $(patsubst $(EXAMPLES_DIR)/%.c,%,$(EXAMPLES_SRC))
 
-# Compare cmd arguments; if `test`, extend it to handle unit tests
+# If `test` is passed as a cmd argument, extend flags to handle unit tests 
 ifeq ($(MAKECMDGOALS), test)
     CFLAGS += -DRUN_UNIT_TESTS
-    SRC = $(wildcard $(SRC_DIR)/*.c) $(TEST_SRC)
     TARGET = test/test
+    SRC = $(wildcard $(SRC_DIR)/*.c) $(TEST_SRC)
+else
+    TARGET = $(EXAMPLES)
+    SRC = $(wildcard $(SRC_DIR)/*.c)
 endif
 
 OBJECTS = $(SRC:%.c=%.o)
-RM = rm -rf
 
-all: $(TARGET)
+# What to do by default (no arguments)
+all: $(EXAMPLES)
 
-$(TARGET): $(OBJECTS)
-	$(CC) $(OBJECTS) -o $(TARGET) $(LDFLAGS)
+$(EXAMPLES): %: $(EXAMPLES_DIR)/%.c $(wildcard $(SRC_DIR)/*.c)
+	$(CC) $(CFLAGS) $(SRC_DIR)/*.c $< -o $@ $(LDFLAGS)
 
-%.o: %.cpp
+%.o: %.c
 	$(CC) $(CFLAGS) -c $< -o $@
 
+# Phony to always rerun it
+.PHONY: test
+
 test: $(TARGET)
 	./$(TARGET)
 
 .PHONY: clean
 
+RM = rm -rf
 clean:
-	$(RM) $(TARGET)
-	$(RM) $(SRC_DIR)/*.o
-	$(RM) $(TARGET).o
-	$(RM) test/*.o
+	$(RM) $(EXAMPLES) $(SRC_DIR)/*.o test/*.o

main.c → examples/01_particle_sim.c

@@ -3,7 +3,10 @@
 #include <limits.h>
 #include <stdlib.h>
 #include <time.h>
-#define NPARTICLES 200 // make sure it's less than the visualiser's capacity
+
+#ifndef NPARTICLES
+#define NPARTICLES 300
+#endif
 
 // assuming max > 0
 #define ABS(x) (x)