:root {
    --primary-color: #2e7d32;
    --primary-color-dark: #1b5e20;
    --primary-color-light: #e8f5e9;
    --secondary-color: #4caf50;
    --text-color: #212121;
    --text-color-light: #5f5f5f;
    --background-color: #ffffff;
    --border-color: #e0e0e0;
    --border-radius: 4px;
    --shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

/* --- dark mode support --- */
@media (prefers-color-scheme: dark) {
    :root {
        --primary-color: #66bb6a;
        --primary-color-dark: #388e3c;
        --primary-color-light: #2e2e2e;
        --secondary-color: #81c784;
        --text-color: #e0e0e0;
        --text-color-light: #bdbdbd;
        --background-color: #1c1c1c;
        --border-color: #424242;
    }

    input {
        background-color: #333;
        color: var(--text-color);
        border-color: var(--border-color);
    }
}

/* --- general, accessibility --- */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
        Helvetica, Arial, sans-serif;
    line-height: 1.6;
    background-color: var(--background-color);
    color: var(--text-color);
    font-size: 16px;
    padding-bottom: 4rem;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* --- Links --- */
section a {
    color: var(--primary-color-dark);
    text-decoration: underline;
    text-decoration-thickness: 1px;
}
section a:hover {
    color: var(--primary-color);
}
@media (prefers-color-scheme: dark) {
    section a {
        color: var(--primary-color);
    }
    section a:hover {
        color: var(--secondary-color);
    }
}

/* --- layout, header/footer --- */
header {
    background-color: var(--primary-color-light);
    border-bottom: 2px solid var(--border-color);
    padding: 1.5rem 2rem;
    text-align: center;
}

header h1 {
    color: var(--primary-color-dark);
    font-size: 2rem;
    margin-bottom: 0.25rem;
}

header p {
    color: var(--text-color-light);
    font-size: 1rem;
}

@media (prefers-color-scheme: dark) {
    header h1 {
        color: var(--primary-color);
    }
}

footer {
    text-align: center;
    padding: 1.5rem;
    margin-top: 2rem;
    color: var(--text-color-light);
    font-size: 0.875rem;
    border-top: 1px solid var(--border-color);
}

.container {
    max-width: 900px;
    margin: 2rem auto;
    padding: 0 1rem;
    display: grid;
    gap: 2.5rem;
}

/* --- form --- */
#grade-form {
    display: grid;
    gap: 2.5rem;
}


/* --- sections --- */
section {
    background-color: var(--background-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
}

section h2 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
    border-bottom: 2px solid var(--primary-color-light);
    padding-bottom: 0.5rem;
}

section p {
    color: var(--text-color-light);
    margin-bottom: 1rem;
    line-height: 1.7;
}

p.note {
    font-size: 0.875rem;
    color: var(--text-color-light);
    margin-top: 0.5rem;
    margin-bottom: 0;
}

fieldset {
    border: none;
}

/* --- results display --- */
.results-section {
    text-align: center;
    background-color: var(--primary-color-light);
    border-color: var(--primary-color);
}

.results-display {
    display: flex;
    justify-content: center;
    align-items: baseline;
    gap: 1.5rem;
    margin: 1rem 0;
    flex-wrap: wrap;
}

.grade-percentage {
    font-size: 4rem;
    font-weight: 700;
    color: var(--primary-color-dark);
}

.grade-letter {
    font-size: 2.5rem;
    font-weight: 500;
    color: var(--text-color-light);
    padding: 0.5rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
}

@media (prefers-color-scheme: dark) {
    .grade-percentage {
        color: var(--primary-color);
    }
    .grade-letter {
        color: var(--text-color-light);
        border-color: var(--border-color);
    }
}

#grade-breakdown h3 {
    font-size: 1.1rem;
    margin-top: 1.5rem;
    margin-bottom: 0.5rem;
    color: var(--primary-color-dark);
}

@media (prefers-color-scheme: dark) {
    #grade-breakdown h3 {
        color: var(--primary-color);
    }
}

#grade-breakdown ul {
    list-style: none;
    padding: 0;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.5rem;
    max-width: 500px;
    margin: 0 auto;
}

#grade-breakdown li {
    background: var(--background-color);
    padding: 0.5rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    font-size: 0.95rem;
}

/* --- score list --- */
.score-list {
    display: grid;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.score-row {
    display: grid;
    grid-template-columns: 1fr auto 1fr auto;
    gap: 0.5rem;
    align-items: center;
}

.score-row label {
    display: none;
}

.score-row input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

.score-row span {
    color: var(--text-color-light);
    font-size: 1.25rem;
    padding: 0 0.25rem;
}

/* --- exam grid --- */
.exam-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 1rem;
}

.input-group,
.input-group-full {
    display: flex;
    flex-direction: column;
}

.input-group label,
.input-group-full label {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-color-light);
    margin-bottom: 0.25rem;
}

.exam-input-row {
    display: flex;
    align-items: baseline;
    gap: 0.5rem;
}

.exam-input-row input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    flex-grow: 1;
    flex-shrink: 1;
    flex-basis: 80px;
    max-width: 140px;
    min-width: 60px;
}

.exam-input-row span {
    color: var(--text-color-light);
}

.input-group-full input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

/* --- buttons --- */
.btn,
.btn-add,
.btn-remove {
    display: inline-block;
    background-color: var(--primary-color);
    color: #ffffff;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    text-align: center;
    transition: background-color 0.2s ease, transform 0.1s ease;
}

.btn:hover,
.btn-add:hover,
.btn-remove:hover {
    background-color: var(--primary-color-dark);
}

.btn:active,
.btn-add:active,
.btn-remove:active {
    transform: scale(0.98);
}

.btn-add {
    background-color: var(--secondary-color);
}

.btn-remove {
    background-color: #d32f2f;
    color: #ffffff;
    padding: 0.5rem 0.75rem;
    font-size: 0.875rem;
    line-height: 1;
}

.btn-import {
    background-color: #5f5f5f;
}
.btn-import:hover {
    background-color: #424242;
}

.button-group {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* --- input number arrows --- */
input[type="number"] {
    -moz-appearance: textfield;
    appearance: textfield;
}
input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

/* --- responsive media queries --- */
@media (max-width: 600px) {
    .container {
        margin-top: 1rem;
        gap: 1.5rem;
    }
    
    #grade-form {
        gap: 1.5rem;
    }

    #grade-breakdown ul {
        grid-template-columns: 1fr;
    }

    .results-display {
        flex-direction: column;
        align-items: center;
        gap: 0.5rem;
    }

    .grade-percentage {
        font-size: 3rem;
    }

    .grade-letter {
        font-size: 2rem;
    }
    
    .score-row {
       grid-template-columns: 1fr auto;
       gap: 0.75rem;
    }
    .score-row input[data-type="score"] {
        grid-column: 1;
        grid-row: 1;
    }
     .score-row span {
        grid-column: 2;
        grid-row: 1;
        align-self: center;
    }
    .score-row input[data-type="possible"] {
        grid-column: 1;
        grid-row: 2;
    }
    .score-row button {
        grid-column: 2;
        grid-row: 2;
        align-self: center;
        padding: 0.75rem;
    }
}