# tk_vector_field.py

# tk_vector_field.py

import math, random, tkinter as tk

WIDTH, HEIGHT = 1200, 600
MARGIN = 40
NUM_LON = WIDTH // MARGIN
NUM_LAT = HEIGHT // MARGIN
DELAY = 10
LENGTH = MARGIN * 0.7

focus = []
for _ in range(20):
    theta = random.uniform(0, 2*math.pi)
    speed = random.uniform(0.5, 3.0)
    vx = math.cos(theta) * speed
    vy = math.sin(theta) * speed
    focus.append({
        "x": random.randint(0, WIDTH),
        "y": random.randint(0, HEIGHT),
        "vx": vx,
        "vy": vy,
        "theta": theta
    })

MAX_SPEED = 10
ACCEL = 0.5

def lon_to_x(lon): return MARGIN + (lon + 180) * (WIDTH - 2*MARGIN) / 360
def lat_to_y(lat): return HEIGHT - MARGIN - (lat + 90) * (HEIGHT - 2*MARGIN) / 180

def magnitude_color(mag):
    r = int(255 * mag); b = int(255 * (1-mag)); g = 40
    return f"#{r:02x}{g:02x}{b:02x}"

def update_focus():
    for f in focus:
        f["theta"] += random.uniform(-0.1, 0.1)
        ax = math.cos(f["theta"]) * ACCEL + random.uniform(-0.1, 0.1)
        ay = math.sin(f["theta"]) * ACCEL + random.uniform(-0.1, 0.1)
        f["vx"] += ax; f["vy"] += ay
        speed = math.sqrt(f["vx"]**2 + f["vy"]**2)
        if speed > MAX_SPEED:
            f["vx"] = f["vx"] / speed * MAX_SPEED
            f["vy"] = f["vy"] / speed * MAX_SPEED
        f["x"] += f["vx"]; f["y"] += f["vy"]

        if f["x"] < 0: f["x"] += WIDTH
        if f["x"] >= WIDTH: f["x"] -= WIDTH
        if f["y"] < 0: f["y"] += HEIGHT
        if f["y"] >= HEIGHT: f["y"] -= HEIGHT

def animate_field():
    update_focus()
    for j in range(NUM_LAT):
        lat = -90 + j*(180/(NUM_LAT-1))
        py = lat_to_y(lat)
        for i in range(NUM_LON):
            lon = -180 + i*(360/(NUM_LON-1))
            px = lon_to_x(lon)
            u = v = 0
            for f in focus:
                dx = (f["x"] - px + WIDTH/2) % WIDTH - WIDTH/2
                dy = (f["y"] - py + HEIGHT/2) % HEIGHT - HEIGHT/2
                dist = math.sqrt(dx*dx + dy*dy) + 1e-6
                u += dx / (dist**2)
                v += dy / (dist**2)
            mag = math.sqrt(u*u + v*v)
            if mag > 0:
                u /= mag
                v /= mag
                dx = LENGTH * u
                dy = -LENGTH * v
                x2, y2 = px + dx, py + dy
                color = magnitude_color(min(1.0, mag/5.0))
                c.coords(arrows[j][i], x2, y2, px, py)
                c.itemconfig(arrows[j][i], fill=color)
    c.after(DELAY, animate_field)

root = tk.Tk()
root.title("# tk_vector_field.py")
root.geometry('+0+0')
c = tk.Canvas(root, width=WIDTH, height=HEIGHT, bg="white")
c.pack()
arrows = [[c.create_line(0,0,0,0,arrow=tk.LAST,width=2) for i in range(NUM_LON)] for j in range(NUM_LAT)]
animate_field()
root.mainloop()