:root {
    /* dark mode */
    --background: #16161a;
    --headline: #fffffe;
    --paragraph: #94a1b2;
    --input-bgr: #242629;
    --button: #7f5af0;
    --btn-text: #fffffe;
    --stroke: #010101;
    --main: #fffffe;
    --highlight: #7f5af0;
    --secondary: #72757e;
    --tertiary: #2cb67d;
    
    /* dark mode sunrise/sunset section  */
    --background-ss: #242629;
    --headline-ss: #fffffe;
    --subheading: #94a1b2;
    --card-bgr: #16161a;
    --card-heading: #fffffe;
    --card-paragraph: #94a1b2;
    --stroke-ss: #010101;
    --main-ss: #fffffe;
    --highlight-ss: #7f5af0;
    --secondary-ss: #72757e;
    --tertiary-ss: #2cb67d;
    
    /* light mode  */
    --background-l: #fffffe;
    --headline-l: #2b2c34;
    --paragraph-l: #2b2c34;
    --button-l: #6246ea;
    --btn-text-l: #fffffe;
    --stroke-l: #2b2c34;
    --main-l: #fffffe;
    --highlight-l: #6246ea;
    --secondary-l: #d1d1e9;
    --tertiary-l: #e45858;
    
    /* light mode sunset/sunrise section  */
    --background-l-ss: #fffffe;
    --headline-l-ss: #2b2c34;
    --subheading-l-ss: #2b2c34;
    --card-bgr-l-ss: #d1d1e9;
    --card-heading-l-ss: #2b2c34;
    --card-paragraph-l-ss: #2b2c34;
    --stroke-l-ss: #2b2c34;
    --main-l-ss: #fffffe;
    --highlight-l-ss: #6246ea;
    --secondary-l-ss: #d1d1e9;
    --tertiary-l-ss: #e45858;

    /* Transition */
    --transition-speed: 0.3s;
}

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', sans-serif;
    line-height: 1.6;
    transition: background-color var(--transition-speed), color var(--transition-speed);
}
input {
    outline: none;
}

/* Theme Switching */
[data-theme="dark"] {
    background-color: var(--background);
    color: var(--paragraph);

    /* Header Styles */
    & header {
        background-color: var(--background);
    }

    & .header-nav a {
        color: var(--headline);
    }

    & .header-nav a:hover {
        color: var(--highlight);
    }

    & #search {
        background-color: var(--input-bgr);
        border-color: var(--stroke);
        color: var(--headline);
    }

    & #submit-btn {
        background-color: var(--button);
        color: var(--btn-text);
    }
    & .sleep-time-section {
        background-color: var(--input-bgr);
    }
    & #sleep-time-input {
        background-color: var(--input-bgr);
        border-color: var(--paragraph);
        color: var(--headline);
    }
    /* Sunrise/Sunset Section */
    & .sunrise-sunset {
        background-color: var(--background-ss);
        color: var(--subheading);
    }
}

[data-theme="light"] {
    background-color: var(--background-l);
    color: var(--paragraph-l);

    /* Header Styles */
    & header {
        background-color: var(--background-l);
    }

    & .header-nav a {
        color: var(--headline-l);
    }

    & .header-nav a:hover {
        color: var(--highlight-l);
    }

    & #search {
        background-color: var(--background-l);
        border-color: var(--stroke-l);
        color: var(--headline-l);
    }

    & #submit-btn {
        background-color: var(--button-l);
        color: var(--btn-text-l);
    }
    & .sleep-time-section {
        background-color: rgba(255,255,255,0.1);
    }
    /* Sunrise/Sunset Section */
    & .sunrise-sunset {
        background-color: var(--background-l-ss);
        color: var(--subheading-l-ss);
    }
}

/* Header Styles */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.logo-wrapper {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.logo-wrapper img {
    width: 50px;
    height: 50px;
}

.logo-wrapper p {
    font-weight: 600;
    font-size: 1.2rem;
}

.header-nav {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.header-nav a {
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-speed);
}

#search {
    padding: 0.5rem;
    border: 1px solid;
    border-radius: 4px;
}

.light-dark {
    cursor: pointer;
}

.current-time-div {
    font-size: 1.2rem;
    font-variant-numeric: tabular-nums;
    letter-spacing: 1px;
}

/* Main Content */
main {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1rem;
}
.sleep-time-section {
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

fieldset {
    border: 1px solid;
    border-radius: 8px;
    padding: 1.5rem;
}

legend {
    font-weight: 600;
    padding: 0 0.5rem;
}

label {
    display: block;
    margin-bottom: 1rem;
}

#sleep-time-input {
    width: 100%;
    padding: 0.75rem;
    margin-bottom: 1rem;
    border: 1px solid;
    border-radius: 4px;
}

#submit-btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    transition: opacity var(--transition-speed);
}

#submit-btn:hover {
    opacity: 0.9;
}

/* Sunrise/Sunset Section */
.sunrise-sunset {
    margin-top: 2rem;
    text-align: center;
    padding: 1.5rem;
    border-radius: 8px;
}

/* Responsive Design */
@media screen and (max-width: 768px) {
    header {
        flex-direction: column;
        gap: 1rem;
    }

    .header-nav {
        flex-wrap: wrap;
        justify-content: center;
    }
}

/* Accessibility Enhancements */
@media (prefers-reduced-motion: reduce) {
    * {
        transition: none !important;
    }
}